Question

Elimination 4x-7y=5 9x-7y=-15

Answer 1

Answer:

x = -4

Step-by-step explanation:

To make this easier to explain and easier to solve, we're going to first multiply the second equation of 9x-7y=-15 by -1 to make the y coefficient positive.

This results in -9x+7y=15.

When we line up the two equations on top of each other now, we'll see that both the first and second equations have opposite y coefficients, which is vital for elimination.

The next step is to add the second equation to the first one. Teachers may tell you to subtract, but I find it easier to add if you make the two y coefficients of negative value to each other.

    4x-7y=5

+ -9x+7y=15

___________

   -5x+0y=20, or just -5x=20, because you have successfully eliminated the y         variable.

From there, you're going to solve like a normal equation (divide both sides by -5) toget you x=-4.