SOLUTION: How to solve this linear system shown by using an elimination strategy: 5x - 4y= -3 2x + 7y= 5 I tries my best, please correct it if i did anything wrong: (5x - 4y= -3)

Algebra ->  Coordinate Systems and Linear Equations  -> Lessons -> SOLUTION: How to solve this linear system shown by using an elimination strategy: 5x - 4y= -3 2x + 7y= 5 I tries my best, please correct it if i did anything wrong: (5x - 4y= -3)      Log On


   



Question 962793: How to solve this linear system shown by using an elimination strategy:
5x - 4y= -3
2x + 7y= 5

I tries my best, please correct it if i did anything wrong:
(5x - 4y= -3) * 2
(2x + 7y= 5) * 5
= 10 - 8y= -6
=10x + 35y= 25
= -43y = -31
y= -31/43
y=0.7

5x - 4y= -3
5x - 4 (0.7)= -3
5x - 2.8= -3
5x=-0.2
x = -0.04

But when I try to verify , it wrong. help please?

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

5x+-+4y=+-3
2x+%2B+7y=+5
-----------------------
5x+-+4y=+-3.....both sides multiply by 2
2x+%2B+7y=+5.....both sides multiply by 5
--------------------------------
10x+-+8y=+-6
10x+%2B+35y=+25
------------------
10x+-+8y-10x-35y=+-6-25
-43y=+-31
y=+-31%2F-43
highlight%28y=+31%2F43%29.....exact solution
highlight%28y=+0.72%29......approximate solution

now, use exact solution of y to find x
2x+%2B+7y=+5
2x+%2B+7%2831%2F43%29=+5
2x+%2B+217%2F43=+5
2x+=+5-217%2F43
2x+=+215%2F43-217%2F43
2x+=+-2%2F43
x+=+-cross%282%29%2F%28cross%282%29%2A43%29
highlight%28x+=+-1%2F43%29.....exact solution
highlight%28x+=+-0.023%29......approximate solution