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ACT Math 3.3 Elementary Algebra 233 Views


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Description:

ACT Math Section: Elementary Algebra Drill 3, Problem 3. Solve for x.

Language:
English Language

Transcript

00:03

And here is your shmoop de jour.

00:05

Solve for x: x squared plus 6x plus 8 equals 0

00:09

And here are the potential answers...

00:16

OK. Any time we see equations in this format -- where there's an x squared then and

00:21

x then an integer -- odds are high that they're asking us to factor.

00:25

What 2 numbers can be multiplied to get 8... and can also be added to get 6?

00:31

Well, the factors of 8 are 1 and 8; that won't work...

00:38

...what about 2 and 4? Ding ding ding!

00:40

So... 2 times 4 is 8... and 2 PLUS 4 is 6... so we can just rewrite the factored version as

00:49

The quantity x plus 2 times the quantity x plus 4... equals zero.

00:54

Now if either of these guys is 0, the whole equation is zero because zero times anything...

00:59

is zero. Yeah, it brings everyone else down to its level.

01:00

So if x is negative 2, this part is 0... and if x is negative 4, this part is 0.

01:06

x has to be one of those answers... and OUR answer here is either A or B... which is...

01:11

option D. Done

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