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ACT Mathematics Videos 164 videos

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ACT Math 6.1 Elementary Algebra 214 Views


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Description:

ACT Math: Elementary Algebra Drill 6, Problem 1. Which of the following is not a factor of x 3 – x?

Language:
English Language

Transcript

00:02

And here's another shmoop du jour... Which of the following is not a factor of

00:06

x cubed minus x?

00:08

And here are the potential answers...

00:14

Okay can we factor?

00:15

Here, the common element on both sides of the minus sign is x.

00:19

If we pull out that x...

00:20

...we get x times the quantity x squared minus 1.

00:24

But now we have x squared minus 1... it's a magic number we should recognize.

00:29

X squared minus 1 is a factorable beast...

00:33

...in quantity x plus 1 times quantity x minus 1.

00:38

So the factors are x... then quantity x plus 1... then quantity x minus 1.

00:43

If we look down our answers list, the only factor left that ISN'T an element of this

00:47

equation is x squared plus 1...

00:49

... so the answer is... E.

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