SOLUTION: I need help with this problem. Solve the following system of equations, using the elimination method: 4x + 3y = -4 3x - 7y = 34

Algebra ->  Linear-equations -> SOLUTION: I need help with this problem. Solve the following system of equations, using the elimination method: 4x + 3y = -4 3x - 7y = 34      Log On


   

Question 689964: I need help with this problem.
Solve the following system of equations, using the elimination method:
4x + 3y = -4
3x - 7y = 34
Answer by Stitch(470) About Me  (Show Source):
You can put this solution on YOUR website!
Given:4X+%2B3Y+=+-4 & 3X+-+7Y+=+34
Set both equations equal to zero
4X+%2B+3Y+%2B+4+=0 & 3X+-+7Y+-+34+=+0
Multiply the first equation by 3
12X+%2B+9Y+%2B+12+=+0
Multiply the second equation by 4
12X+-+28Y+-+136+=+0
We did that multiplication to get the X variables to a common number (12)
Since both equations equal zero, we can set them equal to each other
12X+%2B+9Y+%2B+12+=+12X++-+28Y+-+136
Subtract 12X from both sides
9Y+%2B+12+=+-28Y+-+136
Add 28Y to both sides
37Y+%2B+12+=+-136
Subtract 12 from both sides
37Y+=+-148
Divide both sides by 37
highlight%28Y+=+-4%29
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Now plug -4 into one of the given equations for Y
4X+%2B3Y+=-4
4X+%2B+3%2A%28-4%29+=+-4
4X+-+12+=+-4
Add 12 to both sides
4X+=+8
Divide both sides by 4
highlight_green%28X+=+2%29