Question

I will fan and medal!
5x+7y=31
2x+4y=16

Which of the following systems could be used to solve the given system of equations by the addition method?

10x + 14y = 31 and -10x - 20y = 16
10x + 14y = 62 and 10x + 20y = 32
-10x - 14y = -62 and 10x + 20y = 80

Answer 1

im not quite sure what your asking, do you mean which of the bottom system of equations give you the same value as the top system of equations?

Answer 2

yes i think so @Jdosio

Answer 3

When you solve a system of equations with the addition method, you want the sign you are getting rid of to be opposite on top and bottom. So for example, 5x and -5x. So we can get rid of one of the choices immediately.

Answer 4

okay, we can get rid of the 2nd one @LegendarySadist

Answer 5

Yep. Now look at the other two. See which one of them has a mistake in how it was solved.

Answer 6

Im not sure how to figure that out @LegendarySadist

Answer 7

I'm having a hard time trying to figure out how to explain it as well /:

Answer 8

oh well thank you for your help anyways! @LegendarySadist

Answer 9

Sorry I couldn't be of more help. As a hint, look at the first choice's numbers after the = sign.

Answer 10

A bigger hint: Look closely at the last one.

Answer 11

What do you get when you add them?