Solve the following systems of linear equations, showing all work: -5y+9x=27       8y-x=-70

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-5y + 9x=27

8y - x=-70

First find opposites.

You can do this by multiplying the second equation by 9 getting

72y - 9x = -630

Now add this to the first equation. (Add the y terms together, the x terms together and the constants together.  You should find the x terms cancel each other out.)

-5y + 9x=27

72y - 9x = -630

67y = -603

y = -9

Now that you know the value of y, plug the value into both equations...hopefully getting the same answer.

-5(-9) + 9x = 27    8(-9) -x = -70

45 + 9x = 27             -72 - x = -70

9x = -18                     - x = 2

x = -2                           x = -2

Your point of intersection is (-2, -9).  This is also your solution to the system.

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