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ACT Math 3.4 Elementary Algebra 235 Views


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Description:

ACT Math Elementary Algebra Drill 3, Problem 4. Solve for y in this equation.

Language:
English Language

Transcript

00:02

For a good time, solve this shmoopy question... Solve for y: 2y squared plus 7y plus 3 equals 0

00:10

And here are the potential answers...

00:15

Ok. It's just a basic factoring question. It's in the form of something squared plus something

00:20

plus an integer equals zero.

00:22

A bell should be going off when we see an equation like this.

00:25

We just have to figure out what the factors are... and there's a bit of a curveball in

00:29

here in that there's a 2 on the front end.

00:32

So we know that one of the factors is going to be a 2, as in:

00:35

The quantity 2y plus something times the quantity y plus something.

00:38

Let's plug in some numbers to get the 3. It's kind of easy because 3 only has 2 factors:

00:44

1 and 3...

00:46

Now we have quantity 2y plus 1 times quantity y plus 3.

00:50

If we multiply it out, we get 2y times y here, which is 2y squared.

00:55

Then we have 2y times 3, which is 6y

00:57

plus y times 1, which is just... y.

01:01

6y plus y is 7y; then, 1 times 3 is just 3 so we're done.

01:07

But now... how do we make the whole thing equal to zero? Well, one of the elements here

01:11

has to BE zero.

01:14

If y is negative 3 then this one is 3 minus 3 which is 0...

01:20

...and here, it's just negative one half, because negative 1 half times 2 is negative

01:24

1... and negative 1 plus positive 1 is zero.

01:27

So the other answer is negative one half and the answer is A and C...

01:31

...or option E.

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