Question

MEDAL AND FAN: NEED SOME HELP!!! PLEASE!!!

What is the value of x in the solution to the following system of equations?
x − y = −3
x + 3y = 5

Answer 1

Have you considered subtracting one from the other?

Answer 2

I'm confused on how to do this, please help?

Answer 3

subtract term by term
x - x = 0 so we ewliminate the x

Answer 4

x - y = -3
x + 3y = 5

x-x = 0
-y - 3y = ?

-3 - 5 = ?

Answer 5

that will leave with an equation in one unknown (y) which you can easily solve

Answer 6

what is -3-5 ?

Answer 7

-8?

Answer 8

Is that the answer? -8?

Answer 9

They are so nicely lines up. Think how you would do this.

8 cats + 9 dogs + 14 squirrels

Now, subtract

3 squarrels + 3 cats + 2 dogs

You wouldn't DREAM of subtracting the dogs from the cats, would you? Dogs just aren't cats.

Same things here.

x − y = −3
x + 3y = 5

Subtracting,
consider the xs separately.
consider the ys separately.
consider the constants separately

Actually, I don't like subtraction. Multiply the bottom one by -1 and add.

x − y = −3
-x - 3y = -5

0 - 4y = -8

Much nicer.

Answer 10

Thank you both!

Answer 11

Well, that only finds the value of y. You need the value of x. It would have been smarter to multiply the first equation by 3 and then add

Here's where we started.

x − y = −3
x + 3y = 5

Multiple the first by 3

3x − 3y = −9
x + 3y = 5

Add

4x + 0 = -4

And it's pretty easy to find x from there.