SOLUTION: Please help me solve this system of equations by the addition method: 6x+9y=-41 15x-6y=40 I tried to solve the problem but I came up with using a different number for each

Algebra ->  Coordinate Systems and Linear Equations  -> Lessons -> SOLUTION: Please help me solve this system of equations by the addition method: 6x+9y=-41 15x-6y=40 I tried to solve the problem but I came up with using a different number for each      Log On


   

Question 410101: Please help me solve this system of equations by the addition method:
6x+9y=-41
15x-6y=40
I tried to solve the problem but I came up with using a different number for each equation. I know you have to use the same number for both equations.
Thanks for your help!
Vanessa
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
solve this system of equations by the addition method:
6x + 9y = -41
15x - 6y = 40
:
Multiply the 1st equation by 2, multiply the 2nd equation by 3, results
12x + 18y = -82
45x - 18y = 120
--------------------addition eliminates y, find x
57x = 38
x = 38%2F57
:
Find y using the 1st original equation
6(38%2F57) + 9y = -41
228%2F57 + 9y = -41
9y = -41 - 228%2F57
9y = -2337%2F57 - 228%2F57
9y = -2565%2F57
which is, fortunately:
9y = -45
y = %28-45%29%2F9
y = -5
:
Summarize: x=38%2F57; y = -5
:
:
See if that works in the 2nd equation
15x - 6y = 40
15(38%2F57) - 6(-5) = 40
570%2F57) + 30 = 40
10 + 30 = 40; so these solutions for x and y are correct