Expert: Abe Mantell - 7/8/2011

Question
Hi!
I do not understand the Elimination method. Please help me, Can you go step by step?

x-2y=12
3x-5y=8

4x-9y=61
10x+3y=25

Thank you so much!

Answer
Hello Cecilia,

The elimination method involves adding or subtractin multiples
of the equations so that one of the variables gets "eliminated"
and we can solve for the other.

x-2y=12, let's multiply this by -3, so that when we add this equation
to the 2nd one, the x's will be "eliminated" and we can solve for y.

Thus, we get
-3x+6y=-36 added to
3x-5y=8
=======
0+y=-28, so y=-28, now we can substitute y=-28 for y and solve for x
(or so elimination again to "eliminate" the y's and solve for x)
x-2(-28)=12 ==> x+56=12 ==> x=-44

Try this for the other problem, you should get x=4 and y=5.

Let me know if you need more help.

Abe