Solve system by elimination

Question

-3x-9y=6

-8x+9y=-17

Answer 1

-3x - 9y =  6 -------- (1)

-8x + 9y = -17-------- (2)

 

To eliminate the y value add the equations (1) and (2).

-3x - 9y = 6

-8x + 9y = -17

_________

-11x = -11

Divide each side by -11.

x = 1

Substitute the x value in (1).

-3(1) - 9y = 6

-3 - 9y = 6

Add 3 to each side.

-3 - 9y + 3 = 6 + 3

-9y = 9

Divide to each side by -9.

-9y/-9 = 9/-9

⇒ y = -1

Solution is x = 1, y = -1.