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hello there and welcome to
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our new lesson this video is for senior
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high school
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general mathematics for grade 11.
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prepare the following a paper and a pen
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for you to write your answers or
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solutions
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for the problems later on and remember
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you can always pause and play this video
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whenever necessary you can even go back
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or revisit the portion of this video to
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clarify some things
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for mastery purposes i hope that you are
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all excited for this so let's hop in
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this video presentation is for the first
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quarter
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module 1 of our subject general
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mathematics
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for grade 11. the topic is
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real life functions to be specific
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this is for the first lesson about real
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life functions
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what you need to know we have three main
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objectives for this
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session the first one is we are going to
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determine functions and relations
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second illustrate functions through
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mapping diagrams
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sets and graphs and finally you're going
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to represent
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real life situations using functions
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what's in what you see on the screen
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right now
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is a crossword puzzle exactly
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we have here five descriptions of
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different terms
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that is related to your junior high
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school mathematics
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these are necessary terms for us to
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proceed with our new lesson
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okay so you can pause this video
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and try to recall those important terms
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i'll give you time go ahead pause the
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video
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are you done that sounds great so let's
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reveal the answers so for number one
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let's have number one down
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a rule that relates values from a set of
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values which we call as domain
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to a second set of values which we call
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as range
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what do you think the answer is
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relation so let's put it in our
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crossword puzzle
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relation there
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number three three down blank
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pair pair of objects taken
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in a specific order what do you call
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this
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blank pair the answer is it's an
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ordered pair very good so let's put it
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in our crossword puzzle now to clarify
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about
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ordered pairs we have here an example
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remember that ordered pairs are a
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sequence of two elements
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like for this example one and two they
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are enclosed in a parenthesis and they
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are separated by a comma
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okay that's an ordered pair let's
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proceed to the next one
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how about across number two the set of
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all x or input values can you recall
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you have there your clues o and i for
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the second and the second to the last
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letter
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and the answer is domain right
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brilliant domain let's review about
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domain
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when we say domain look at the example
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we have four sets
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or we have four ordered pairs in this
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set
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one seven two six three five
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and four four now what is our domain
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here
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our domain are the first elements inside
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the parenthesis or first element in each
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of the ordered pairs
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so that means it's 1 2 3
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and four which serves as our domain
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how about for number four across
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collection of well-defined
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and distinct objects called elements
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that share a common characteristic
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you have this when you're still in grade
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seven the answer is
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well done that's set s84
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set last one
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across number five the set of all y
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or output values what do you call that
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your clue there is it ends with letter e
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you already have the domain this is the
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pair of domain
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that means we are referring to the range
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okay we have completed our crossword
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puzzle but before that let's clarify on
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range
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now using the same example for the
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domain
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we have here this set of ordered pairs
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we already have one two three four as
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our domain earlier right
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now this time the range is these values
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the second element of each ordered pair
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or the y values that will be 7
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6 5 and 4 in this example
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what's new what makes relation
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a function
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a function is a special kind of relation
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because it follows an extra rule
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just like a relation a function is also
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a set of ordered pairs however
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take note of this every x
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value must be associated to
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only one y value i repeat
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every x value must be associated
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to only one y value that's the most
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important part of this lesson
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remember that that's for the definition
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of our function
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illustrations will help us a lot to
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learn
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functions easily so we have here mapping
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sets and graphing a function is a
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special type of relation
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always remember that in which each
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element
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of the domain is paired with exactly
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one element in the range a mapping
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shows how the elements are paired
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it's like a flowchart for a function
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showing the input and the output of
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values
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like this the domain for the first set
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and the range for the second set now in
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this
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mapping let's identify if this is
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a function or not a function how do we
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do that
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recall every x
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value must be associated to
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only one y value so basing on that
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let's try to check if every element in
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our domain
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is associated to only one value in our
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range
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let's focus on this part our domain a
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is associated to roman numeral one
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so that's one is to one that's the
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correspondence
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second domain or second element b
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that is associated to only one
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y value that is roman numeral 2.
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here c third element
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of our domain is associated to
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or is being paired to only one value of
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y
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that is 3 or roman numeral 3. and lastly
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d in our domain is being paired
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with roman numeral 4 in our range
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so as you can see every element in our
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domain
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is being paired to only one value
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of y in our range so that
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means this example is
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correct this is a function
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let's look at example number two can you
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identify
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if the given is a function or not a
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function
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you may pause this video
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okay all right so how about this example
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this is still a function y
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looking at all the elements of our
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domain negative 3 is being paired to 0
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negative 1 is being paired to 4 2
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is being paired to 7 and 4 is being
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paired to 4.
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so this shows that every element in our
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domain
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is being mapped or is being paired to
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only one
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value in our range which means
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that if we have an input of negative
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three the output is only zero
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if we have an input of negative one the
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output is
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only four we don't have any other y
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values
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if we have an input of two therefore our
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output is seven
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if our input is four our output is also
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four this type of correspondence shows
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many is the one for this part we have
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two elements in our domain
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here that's negative one and four we
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have two elements in our domain
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that has the same value in our range
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take note
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what we are referring to in a function
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is we have
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every element in our domain is paired
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with
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one element in our range which means
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that for every input there's only one
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output this type of correspondence is
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considered
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as a function i hope that's clear so
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this is
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a function third example how about this
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is this a function or not a function you
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may pause this video
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and let's reveal this is not a function
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why earlier we saw
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many is the one correspondence right
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this time
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you call this type of correspondence
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recall your grade seven
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and grade eight mathematics in your
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junior high school
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this is for this element in our domain
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which is letter a
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it's being paired let's focus on that
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here
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that's our domain a it's being paired to
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one roman numeral 1 in the range at the
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same time
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the same element in the domain is being
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paired to
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roman numeral 3. now that means
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this element in the domain has two
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outputs
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one and three which is clearly a
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violation of the definition of our
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function right
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therefore basing on that element
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this example is
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not a function i hope i made that clear
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a is being paired to two values in our
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range
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we are done with the mapping again these
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are illustrations to help us out
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understand or identify if the given is a
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function
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so this time let's move on to sets sets
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in this example we will have rooster
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notation
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so we have a set of four ordered pairs
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beginning with two three
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four five five six
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and we have six seven now can you
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identify if this given set
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is a function or not a function
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now how do we do that let's identify
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first the x
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and the y elements in each ordered pair
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so for the first one here
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two is our x sub one three
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is our y sub one four is our second
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value of x in the second ordered pair
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five is our y sub two five
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is our x sub three in the third ordered
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pair
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six is our y sub three here
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in the fourth ordered pair this will
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serve as our
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x of four and this will be our y sub
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four which is seven
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now why is it important for us to
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identify
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our x and y's in each of the ordered
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pairs
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because these values in a domain
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are the critical values so identify if
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it's a function or not a function
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why look at this we have 2 4 5
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and 6 in the domain no x value
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is repeated so 2 is distinct from the
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rest of the domain that's
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4 5 and 6. thus we consider
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this as a function
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this set is a function remember that
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when there's no x value that has been
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repeated in the given set
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then that means it's a function second
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example
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this set we have three three four five
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five five and five four so again
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the first step is let's identify the x
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and the y
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elements like this followed by
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yes we are going to identify the domain
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so meaning all the x values in our
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ordered pairs
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we have 3 4 5 and 5.
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now notice that here 5
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is repeated that's the x value it's
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repeated for that element in our x or in
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our domain
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we do have two different outputs which
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is not
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anymore the definition of a function so
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this is
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not a function well done
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we are done with the second illustration
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for sets
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again we are done with mapping and we
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are done with sets now this time let's
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focus
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into another way that's for graphing
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how do we identify if the given graph is
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a function or not
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your clue there is being pointed it's
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vlt
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that would be our magic keyword to
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identify if the graph
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is a function or not how what do you
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mean by
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vlt vlt stands for
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vertical line test
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yes functions can also be determined in
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graphing we can use this vertical line
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test which is a special kind of test
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using imaginary vertical lines
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and to check if these vertical lines
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would touch the graph only
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once otherwise it is not a function
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what do i mean by that if the vertical
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line
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hits two or more points on the graph
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it is not considered a function
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let's look at some examples look at this
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graph
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how would we know if this graph is a
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function
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or not again what's our magic keyword
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we'll be using vlt that's the vertical
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line test
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right so that's it the blue line that
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you see on the screen right now
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that's an imaginary line yeah it's not
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part of the graph
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we just made that line to test if the
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given graph
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is a function or not i hope you're
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following
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so the point there is here which means
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that the line the vertical line touches
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the graph
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at that point only once
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now let's move the blue line let's move
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the blue vertical line
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because here you can check if it's a
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function
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if any point of the graph it would only
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touch
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the graph or the given graph once so
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let's move the vertical line
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how about there yes it only hits or it
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only touches the graph once
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how about there only once and finally
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right here yes it only touches the graph
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once hence we can say that the given
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graph
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is a function so that's an example of a
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function
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basing on the graph
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let's look at another example identify
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if this graph
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is a function or not a function i'll
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give you time
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you may pause this video to give
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yourself more time
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all right are you done let's check let's
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create
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our imaginary vertical line again we
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will be using
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vertical line test right there
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the black dot represents the point where
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in the vertical line touches your given
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wrath
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it's only once right let's move it a
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little bit to the right right there
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it touches the graph how many times
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still once
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let's move it there still once
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last one over there still it touches the
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graph
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once basing on that we can conclude that
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the given graph
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is indeed a function
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so that's an example of a function now
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let's practice more let's identify if
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these given graphs
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are functions or not a function again
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let's identify
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try these graphs you can pause this
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video right now
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and give yourself more time to
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scrutinize each of the graph
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and identify if it's a function or not
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a function go ahead
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[Music]
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okay so let's reveal the answers
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now based on the sixth graph we can
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actually create
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two groups and the first group consists
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of
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these two graphs
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now let's focus on this point
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right here for the first graph as you
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can see
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the vertical line touches the given
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graph once
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how about for the second graph there it
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only touches
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yes it touches the given graph same with
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the first graph
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only once let's try to move the vertical
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line
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to the right right there
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it touches still the same once let's
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move it more
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right there still touch us once
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and last one same result
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once thus we can conclude that these two
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graphs
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are considered as
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very good we consider this as functions
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so the remaining four graphs looks like
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this
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observe for the first graph we have here
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two points
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which means that the vertical line
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touches the graph or touches the given
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graph
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at two points however for the second
00:19:03
graph this would be the first one
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and that would be the second one still
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the same it touches the given graph
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twice
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the vertical line touches the graph here
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at the same time here
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so that means there would be two points
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right and lastly we have here the last
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graph it touches the graph
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twice let's move the vertical line
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like this well observe
00:19:29
that for the fourth graph you now have
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three points
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earlier it was only two this time as we
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move the vertical line it touches the
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graph at three points
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now for the first three graphs it's the
00:19:42
same it touches the given graph twice
00:19:45
let's move it there observe
00:19:48
that in all these given graphs the
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vertical line
00:19:52
touches the given graph more than once
00:19:56
again that's more than once because for
00:19:59
the first second and third graph
00:20:01
it touches the graph twice for the
00:20:03
fourth graph it touched us earlier the
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graph twice
00:20:06
this time thrice it's more than once
00:20:09
yes which makes all of these graphs
00:20:12
not a function so these are examples of
00:20:16
not a function
00:20:20
so those are the illustrations again for
00:20:23
the mapping
00:20:24
sets and graph
00:20:28
how about functions in real life
00:20:31
this is a circle so an example of a
00:20:34
function in real life
00:20:36
is the circumference of a circle the
00:20:39
circumference of a circle
00:20:41
is a function of its diameter it can be
00:20:43
represented as
00:20:45
circumference or c of d is equal to d
00:20:48
pi alternatively we can also use it
00:20:52
as a function of radius which is c of
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r is equal to two pi r
00:20:59
[Music]
00:21:00
another example is a shadow the length
00:21:04
of a person's shadow
00:21:06
along the floor is a function of their
00:21:09
height
00:21:10
and the third example is driving a car
00:21:14
when driving a car your location
00:21:18
is a function of time
00:21:23
what's more i prepared here a 10 item
00:21:27
assessment
00:21:28
first to check your understanding for
00:21:30
our lesson for today
00:21:31
let's try to have a closer look you can
00:21:35
pause this video or you can even take a
00:21:37
screenshot and answer it later during
00:21:39
your available time
00:21:41
so we have your items one two and three
00:21:43
again you may pause or take a screenshot
00:21:46
[Music]
00:21:49
okay let's move on the next set is for
00:21:52
items four to six
00:22:00
next we have seven to nine
00:22:03
again you may take a screenshot or pause
00:22:06
this video
00:22:10
and finally we have item number 10.
00:22:14
[Music]
00:22:18
if you're using the same mode you'll do
00:22:20
not forget to submit your answers to
00:22:22
your teacher on your agreed date and
00:22:24
time
00:22:26
[Music]
00:22:27
what you need to remember a relation
00:22:30
is a function when every x value is
00:22:33
associated to only one y value
00:22:37
do not forget that you can illustrate
00:22:40
functions
00:22:41
through graphing mapping or sets
00:22:45
and lastly functions can be seen in our
00:22:48
daily lives like driving a car
00:22:51
wherein your location is a function of
00:22:54
time
00:22:54
the length of your shadow which is a
00:22:57
function
00:22:57
of one's height and a lot more
00:23:01
and that's it we are done with the first
00:23:03
lesson
00:23:04
for this topic functions for our general
00:23:07
mathematics subject
00:23:09
great job for today see you in the next
00:23:12
lesson