Question

Solve for x and y by substitution 2x+5y=7 -2x+4y=15

Answer 1

I first found x using the second equation :

-2x+4y=15
-2x = -4y+15
x =2y-7.5

Then, I substituted this value into the OTHER equation :

2x+5y=7
2(2y-7.5)+5y=7
4y-15+5y=7
9y=22
y=2.444

So you have you y value. Now, input this value into any one of the other equations (it doesn't matter which) to find x.

-2x+4y=15
-2x+4(2.444)=15
-2x+9.776=15
-2x=5.224
x=-2.612.

So the solution for this system of functions is (-2.612, 2.444).