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ACT Math Videos 161 videos

ACT Math 3.1 Plane Geometry
2559 Views

ACT Math: Plane Geometry Drill 3, Problem 1. What is the area of the trapezoid shape in the video?

ACT Math 2.2 Pre-Algebra
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ACT Math Pre-Algebra: Drill 2, Problem 2. Solve for y.

ACT Math 2.5 Pre-Algebra
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ACT Math Pre-Algebra Drill 2, Problem 5. Given the chart in the video, what is the mode?

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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?

Language:
English Language

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.

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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