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ACT Mathematics Videos 164 videos
ACT Math: Coordinate Geometry Drill 1, Problem 1. Which inequality is expressed by the number line?
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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?
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.
Full Transcript
- 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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