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SAT Math 6.3 Algebra and Functions 212 Views


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Description:

SAT Math 6.3 Algebra and Functions

Language:
English Language

Transcript

00:02

And we're getting math-y with it...

00:04

x + y = 1

00:06

y + z = -4

00:09

x + z = -19

00:12

Using the above equations, what is the value of z?

00:15

And here are the potential answers...

00:20

What we've got here is a system of 3 equations, and 3 variables to solve for.

00:26

The first equation is x + y = 1.

00:28

We can subtract x from both sides to get y = 1 - x.

00:33

Now, let's plug in what we know into the second equation, y + z = -4.

00:38

For example, we can subtract y from both sides to get z = -4 - y.

00:43

What do we do next?

00:46

Or, we can substitute y out of this equation.

00:48

Now we need to define x in terms of z.

00:51

Our last equation can help with that.

00:53

So, let's subtract z from both sides,

00:56

and we will see that x is equal to -19 - z.

01:01

Now we can just substitute x out of our previous equation.

01:04

First, we'll distribute the negative sign into the parentheses.

01:08

Then, we'll do it again for the second pair of parentheses.

01:11

Finally, we'll add z to both sides, and combine the constants.

01:16

After this, we'll divide both sides by 2, and find that z = -12.

01:21

So our answer is (A).

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