Question

Consider the system of linear equations. 5x+10y=15 10x+3y=13 To use the linear combination method and addition to eliminate the x-terms, by which number should the first equation be multiplied?

A- -2
B- -1/2
C- 1/2
D- 2

Answer 1

k = -2 for sure

I normally multiply 5x+10y=15 by -2 to cancel out the x's.

This is because you can only solve the problem if one of your variables is canceled out and then you solve!

Answer 2

A: -2

Explanation:

You want some factor k such that k(5x) +(10x) = 0. That is, 5k+10 = 0. The solution to this is k=-2, corresponding to selection A.