SOLUTION: Solve the system by substitution. 3x – y = –7 x + y = –9

Algebra ->  Graphs -> SOLUTION: Solve the system by substitution. 3x – y = –7 x + y = –9       Log On


   

Question 108316: Solve the system by substitution.
3x – y = –7
x + y = –9
Answer by HyperBrain(694) About Me  (Show Source):
You can put this solution on YOUR website!
x%2By=-9
x=-y-9

3x-y=-7
but, x=-y-9. So,

3%28-x-9%29-y=-7
-3x-27-y=-7
-3x-x-27=-7
-4x-27=7
-4x-27%2B27=-7%2B27
-4x%2B0=20
-4x=20
x=-5
Solving for y,
x%2By=-9
-5%2By=-9
-5%2B5%2By=-9%2B5
0%2By=-4
y=-4

THerefore, x=-5 and x=-4

Power up,
HyperBrain!