SOLUTION: How do I use linear combinations to solve this linear system: y=x-9 x+8y=0 So far I've gotten this far:

Algebra ->  College  -> Linear Algebra -> SOLUTION: How do I use linear combinations to solve this linear system: y=x-9 x+8y=0 So far I've gotten this far:       Log On


   

Question 566516: How do I use linear combinations to solve this linear system: y=x-9
x+8y=0
So far I've gotten this far:
(y-x=-9) 9y=-9 (Divided 9 to each side)
8y+x=o y=-1
I need the other half of the problem where y is eliminated and x is solved so I have two points. Example: (8,-1) This is the solution I just don't know how to get 8. Please help me out, thank you.
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
-1 x + 1 y = -9 .............1
1 x + 8 y = 0 .............2
Eliminate y
multiply (1)by -8
Multiply (2) by 1
8 x -8 y = 72
1 x 8 y = 0
Add the two equations
9 x = 72
/ 9
x = 8
plug value of x in (1)
-1 x + 1 y = -9
-8 + 1 y = -9
1 y = -9 +8
1 y = -1
y = -1