SOLUTION: Could someone please help me with a couple of problems,that I'm having trouble with? These are Systems of equations,and they need to be solved by the Elimination method.Also could

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Question 145138: Could someone please help me with a couple of problems,that I'm having trouble with? These are Systems of equations,and they need to be solved by the Elimination method.Also could you show me how to work them step by step? Thank you very much in advance for your time and all the help.
1)5x - y = 12
3x + y = 4
2)2x - y = -6
2x - 2y = -4
Answer by nerdybill(7384) (Show Source):
You can put this solution on YOUR website!
This site has a good explanation of the "elimination method":
http://www.purplemath.com/modules/systlin6.htm
1)5x - y = 12
3x + y = 4
------------ start by adding both equations together to get rid of the 'y'
8x = 16
x = 2 (dividing both sides by 8)
To find y, substitute x back into either of the two equations:
5x - y = 12
5(2) - y = 12
10 - y = 12
-y = 2
y = -2
2)2x - y = -6
2x - 2y = -4

multiply the second equation by -1 to get:
2)2x - y = -6
-2x + 2y = 4
------------- add both equations together
y = -2
To find x, substitute y back into either of the two equations:
2x - y = -6
2x - (-2) = -6
2x + 2 = -6
2x = -8
x = -4