Question

A: 5x - 2y = 10

B: 4x + 3y = 7
To solve this system of equations by addition, what could you multiply each equation by to cancel out the x-variable A) Multiply A by 3 and B by 2
B) Multiply A by 4 and B by 5
C) Multiply A by -3 and B by 2
D) Multiply A by -4 and B by 5

Answer 1

The answer is D) you could multiply A by -4 and B by 5,

This choice would help you cancel out the x variable so that you could solve for the y. To see this, multiply the x terms by the given amounts.

Equation A (just the x)

5x ----> multiply by the -4 above

5x * -4 = -20x

Equation B (just the x)

4x -----> multiply by the 5 above

4x * 5 = 20x

Since -20x and 20x cancel when adding, these are the numbers that you are looking for.