Question

In order to solve the following system of equations by addition, which of the following could you do before adding the equations so that one variable will be eliminated when you add them? 2x-4y=5
6x-3y=10 please help

Answer 1

A. Multiply the top equation by -3 and the bottom equation by 2.
B. Multiply the top equation by 3 and the bottom equation by 4.
C. Multiply the top equation by -3.
D. Multiply the top equation by -2.

Answer 2

The idea behind solving systems is to get coefficients on terms equal to each other. So, looking at 2x from eq 1. and 6x from eq 2... if I wanted to eliminate them... What would I multiple 2x by before adding them?

Answer 3

-2? @luffingsails

Answer 4

Exactly... that is the only thing you would do. answers A and B only make things worse. answer C doesn't create a helpful coeffiecient. So, D is the right answer.

Answer 5

thank you! that was simple

Answer 6

Sorry, what you wrote (-2) is wrong. You would multiply by -3...! So the right answer is C.

-3 * (2x) = -6x
-6x + 6x = 0... which is what you want to achieve.

Answer 7

dang its ok