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December 17, 2014

December 17, 2014

Posted by **T.T** on Thursday, January 24, 2008 at 10:16pm.

- Math -
**Jin**, Thursday, January 24, 2008 at 10:31pmFirst, try to see if you can cancel out any of the variables by adding the equations.

4x+2y-1 also equals 4x+2y=1

(4x+2y=1)(2) = 8x+4y=2

now, add the two equations and see the y cancel out.

2x-4y=2

8x+4y=2

10x=4

x=4/10=2/5

Plug this number back into the equation (any of those two) and find y.

- Math -
**T.T**, Thursday, January 24, 2008 at 10:54pmi still do see how you got that answer i got 2x-4y=7 ,4x+2y=-1. 6x+6y=6 isn't that how you do it please help understand better

- Math -
**Reiny**, Thursday, January 24, 2008 at 11:26pmT.T

the purpose oft using addition here is to add them in such a way so that one of the variables will cancel out

leave the first equation alone

2x-4y=7, multiply the second by 2

8x+4y=-2, now add them

10x + 0 = 5

x = 1/2

back in the first....

2(1/2)-4y=7

1-4y=7

-4y=6

y=-3/2

You just added them to get 6x+6y=6

Even though that new equation is valid and true it gets you nowhere.

- Math -

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