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good morning today we'll be working on
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in route and rational exponents this is
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a part 1 of two videos this is covering
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teks 2a 7g from algebra 2 this is using
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some Big Ideas algebra 2 math textbook
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chapter 6.1 so we're going to first
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start explaining wasn't what an in route
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is you can extend the concept of a
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square root to other types of roots so a
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square root is and in through it means
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that the root is 2 a cubed root would
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mean that the N is 3 so for example
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since 2 cubed equals 8
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then the cubed root of 8 equals 2
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one of the other ways we're going to
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discuss today is this can be written 8
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to the one-third equals 2 so using the
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TI calculator one of the things we're
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going to point out here is that this
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button right here and depending on your
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calculator will change the color we want
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to select the enth root and so this
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picture right here actually has a little
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in the exponent so it looks like this
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and so in order to select this we have
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to click the control button first so
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we're going to talk about taking the nth
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root of different numbers so number one
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says take the nth root of that number so
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that means we're going to take the cube
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root of negative 216 so we're going to
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use our calculator and we're gonna do
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control and select the in through button
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basically what number to the third power
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gives me negative 216 and the answer is
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negative six we're gonna take the fourth
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root of 81 okay now with any even in
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numbers so if n is even and write this
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down if n is even it has a positive and
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negative solution now what do we mean it
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has a positive or a negative solution
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when my calculator if I go back to this
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one and do the 4th root of 81 the
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q leaders only going to give me the
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positive solution it's gonna tell me
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that the answer is a positive 3 but
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let's think about that positive 3 to the
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fourth power is 81 but go ahead and try
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negative 3 in parenthesis to the 4th
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power doesn't it also give you 81 it
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does so whenever n is even you're going
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to do the positive and the negative
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solution by it again okay so number
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number 3 we're going to take the 4th
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root of 16 what number to the 4th power
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gives you 16 and don't forget if n is
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even it's gonna have a positive and
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negative solution so the 4th root of 16
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is a positive 2 but it's also a negative
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2 okay this 2 here that's the square
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root guys I don't actually have to put
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the 2 if the index so that's that n is
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called an index if the index is a 2 you
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don't have to write it that's what a
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square root is what is the square root
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of negative 49 tried in your calculator
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it actually comes back as there's not a
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real solution there is no number that
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you can square that'll give you a
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negative number so something like this
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would come back no solution the next one
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I'm going to take the cube root of
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negative 125 so what number to the third
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power gives me negative 125 the answer
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is negative 5 and guys the way you check
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that is negative 5 in parentheses to the
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third power it should give you negative
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125 that is correct
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number 6 we're going to take the fifth
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root of 243 what is the 5th
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root of 243 well the answer is three and
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so we check it does three to the fifth
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power
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does it give us 243 and it does so
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that's how we take the nth root of
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problems now let's get into rational
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exponents these ones are gonna be really
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really important I want to explain where
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these letters and numbers come from so
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when you take the square root so we're
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taking the square root of a that number
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on the outside is an imaginary two we
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don't write a two but we see it what it
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is there and it has an exponent of a 1
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so the square root of a could be really
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written as a to the one half so the way
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the fractions work that fraction on the
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top is gonna be your exponent and the
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bottom is going to be your index I wrote
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that better for you so on the numerator
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is the exponent that is gonna stay
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outside of your parenthesis the index is
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what's gonna go inside your radical it's
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called the index so this number right
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here if it's a square root that's a 2 we
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don't see the two but if it's a cube
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root we'll see a 3 there if it's the 4th
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root we'll see a 4 there now negatives
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we're not gonna see a ton of them they
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work almost exactly the same the only
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difference is if you have a negative so
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in algebra 1 we talked about it's an
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exponents a negative it's not happy
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there or like it doesn't belong there so
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if it's a negative you're actually gonna
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put it to the bottom and then it belongs
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there and it turns positive ok so if
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it's a negative we move it to the bottom
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and do exactly what we see so before I
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even move on to the next page so it's
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easier to see while we're on this if I
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have a letter B and I say it's to the
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2/5 power how can we rewrite that well
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we're gonna take the 5th root of B and
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all of that's going to be squared
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okay so the five is the index and that
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index is going to go here the top is my
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exponent and it's gonna stay an exponent
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okay we are going to rewrite in radical
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form and then we're going to evaluate so
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16 to the three-halves is gonna be
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rewritten 16 is my base I'm gonna put a
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radical what goes on the inside of the
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index and what goes on the outside as
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the exponent well as we wrote the index
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is the bottom number the denominator if
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it's a two I do not have to write a two
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in my index that's automatically a
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square root and this is gonna be raised
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to the third power what is the square
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root of 16 which we knew positive
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solutions so the square root of 16
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becomes 4 4 cubed 4 times 4 times 4 is
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gonna be 64 so when you're showing the
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work you're gonna rewrite it first and
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try not using a calculator so number two
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we're gonna start by rewriting it now it
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has a negative exponent if it's a
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negative exponent we're gonna rewrite it
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as 1 over 32 to the 3/5 power okay so on
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my denominator my 32 is going to go
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inside of my radical I'm gonna have a 5
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on the outside that is my index and this
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is going to be raised to the third power
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what is the fifth root of 32 must be a
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really small number what number to the
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fifth power gives us 32 it's 2 so 1 over
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2 cubed 2 times 2 times 2 the answer is
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1/8 again this time we have a 4 4 is my
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base the denominators 2 which makes it a
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square root to the fifth power and guys
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what you're not seeing what you never
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have to do is you don't to put the 2
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they're a square-root already has it too
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well what's the square root of 4 the
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answer is 2 and what is 2 to the fit
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power the answer is 32 okay the next one
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it's a negative exponent if it's a
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negative exponent I'm going to rewrite
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it first with a positive exponent if
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it's negative you're gonna move it to
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the denominator 9 to the 1/2 power means
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it's actually the square root of 9 what
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is the square root of 9 the answer is 3
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now why was it the square root of 9
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because every single problem can have a
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1 exponent every single problem can have
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a 2 index and you don't have to show the
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1 or the 2 okay so anything to the 1/2
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power is just a square root number 581
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and we're gonna do the 4th root of 81
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and whatever we get to the 3rd power
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the 4th root of 81 is 3 so 3 to the 3rd
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power 3 times 3 times 3 is 27 the last
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one 1 is my base it goes inside of my
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radical I'm taking the 8th root of 1 and
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I'm gonna raise it to the seventh power
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okay what's the 8th root of 1 what
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number to the 8th power gives you 1 1 1
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to the 7th is 1
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hopefully this video helped you
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understand a little bit of how to
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rewrite rational exponents as radicals
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and if you like this video if it helped
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you at all please give it a thumbs up
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you can subscribe to this channel well I
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will be posting more educational videos
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thanks and have a great day