Question

One way of solving systems of linear equations is by adding a multiple of one equation to the other. the multiplier for one equation is chosen so that one of the two variables will cancel out in the sum. what should you multiply the equation y=0 by so that when added to x+y=40 the variable y will cancel out?

Answer 1

We want to use elimination to solve
y = 0 (1)
x + y = 40 (2)

Multiply (1) by -1 to eliminate y.
-y = 0 (3)

Add (2) and (3).
x + y + (-y) = 40 + 0
x = 40

Answer: Multiply by -1.