SOLUTION: solve the system by addition -3x+7y=2 x+2y=-18

Click here to see ALL problems on Linear-equations

Question 88462: solve the system by addition
-3x+7y=2
x+2y=-18
Found 2 solutions by checkley75, stanbon:
Answer by checkley75(3666) (Show Source):
You can put this solution on YOUR website!
-3x+7y=2 now multiply the second equation by 3 & add them
3x+6y=-54
------------------------
13y=-54+2
13y=-52
y=-52/13
y=-4 answer
-3x+7*-4=2
-3x-28=2
-3x=2+28
-3x=30
x=30/-3
x=-10 answer.
proof
3*-10+6*-4=-54
-30-24=-54
-54=-54

Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
-3x+7y=2
x+2y=-18
----------
Multiply thru the 2nd equation by 3 to get:
3x+6y=-54
Add that to the 1st equation to get rid of the x terms:
13y = -52
y = -4
----------
Substitute that value of y into x+2y=18 to solve for x:
x - 8 = -18
x = -10
---------------
Check the answers in -3x+7y=2
30-28=2
2 = 2
=================
Cheers,
Stan H