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?
21 – 4y= 5
61 – 31= 10
O A. Multiply the top equation by 3 and the bottom equation by 4.
O B. Multiply the top equation by -3.
C. Multiply the top equation by -2.
D. Multiply the top equation by -3 and the bottom equation by 2.

Answer 1

9514 1404 393

Answer:

B. Multiply the top equation by -3.

Explanation:

We assume your equations are intended to be ...

• 2x -4y = 5
• 6x -3y = 10

Multiplying the top equation by -3 before adding the bottom equation will cancel the x-terms:

-3(2x -4y) +(6x -3y) = -3(5) +(10)

9y = -5 . . . . . x-term is eliminated