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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?
ACT Math: Intermediate Algebra: Drill 3, Problem 1. Find the fifth number in the series.
ACT Math: Pre-Algebra Drill 1.2. What proportion of Jenna's day is spent Wii-swimming?
ACT Math 4.5 Elementary Algebra 492 Views
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Description:
ACT Math: Elementary Algebra Drill 4, Problem 5. What is the solution to the problem shown?
Transcript
- 00:02
And here is your shmoop math question de jour
- 00:07
Multiply the quantity x minus 1 times the quantity x plus 1 times the quantity x minus 1
- 00:13
And here are the potential answers...
- 00:19
OK so what is this question asking?
- 00:22
This one is really about how neat we are.
Full Transcript
- 00:24
No, not how super-terrific and all-over groovy we happen to be,
- 00:28
but how tidy we are in terms of organizing our brute force methods of multiplying distributions.
- 00:35
Start with just the quantity x minus 1 times the quantity x minus 1.
- 00:39
Follow the arrows and we get x times x which is x squared
- 00:44
x times 1 which is x
- 00:46
... then negative 1 times x, which is negative x.
- 00:50
then negative 1 times 1, which is 1.
- 00:54
Now we just take the quantity x minus 1 and multiply it by the simplified x squared minus 1.
- 01:00
We get x times x squared, which is x cubed and note that since we have a cubed here,
- 01:06
we can eliminate 2 of the potential answers.
- 01:09
Now we've got x squared times negative 1, which is negative x squared,
- 01:12
then negative 1 times x which is negative x,
- 01:16
and finally negative 1 times negative 1 which is positive 1.
- 01:19
So the answer is right here: C.
- 01:22
Neat-o.
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