Question

If you wanted to eliminate the y variable by adding the two equations in the following system, what could be your first step?

x − y = 6
4x − 3y = 12

Answer 1

multiplica la primera ecuación por -3 a ambos miembros

Answer 2

-3x +3y=18
4x - 3y=12

Answer 3

you want to take advantage of the fact that x - x = 0 for any x value


So you want to apply this to the y variable


Notice how adding -y to -3y gives you -4y, which is not 0.


So we need to turn -y into +3y, and we do this by multiplying the top equation by -3 (both sides) to get -3x +3y=18


Now notice how 3y+(-3y) = 3y-3y = 0


So the first step would be to multiply both sides of the first equation by -3.