Question

Solve using elimination.
-9x – 9y = 18
-9x - 5y = -18

Answer 1

x = 7, y = -9

Explanation:

Multiply equation (1) by -1 and add to equation (2)

9x + 9y = -18

-9x - 5y = -18

4y = -36

y = -9

-9x - 9(-9) = 18

-9x + 81 = 18

-9x = -63

x = 7

Answer 2

x=7, y=-9

Explanation:

-9x – 9y = 18

-9x - 5y = -18

Multiply the second equation by -1

9x + 5y = 18

Add this to the first equation to eliminate x

-9x – 9y = 18

9x + 5y = 18

---------------------------

-4y =36

Divide each side by -4

-4y/4 = 36/-4

y = -9

Now find x

-9x -9y = 18

-9(x) -9(-9) = 18

-9x +81 = 18

Subtract 81 from each side

-9x +81-81 =18-81

-9x =-63

Divide each side by -9

-9x/-9 = -63/-9

x=7