How do you solve the system of equations -8x - 8y = 8 and - 7x - 8y = 16 using elimination?

2 Answers
Mar 29, 2018

x=8 and y=-9

Explanation:

Both have -8y so we can eliminate it by adding equation:

quad\ quad-8x-8y=8
-quad-7x-8y=16

quadquad\ \ -x quadquadquadquadquad\ = -8

Solving for x would get you x = 8.

Now plug this value into first equation:
-8(8)-8y = 8

-64-8y = 8

-8y = 8+64

-8y = 72

y = -9

So we have x=8 and y=-9

Mar 29, 2018

x=8, y=-9

Explanation:

[[-8x-8y,=,8],[-7x-8y,=,16]]

multiply first row by -1

[[8x+8y,=,-8],[-7x-8y,=,16]]

Now add the rows:

(8-7)x+(8-8)y=-8+16

1x+0y=8

x=8

Now, we can use any row to obtain y:

8x+8y=-8

Using x=8:

8color(red)((8))+8y=-8

64+8y=-8

8y=-8-64

8y=-72

y=-72/8

y=-9