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March 29, 2017

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Solve the system by addition 2x-4y=7,4x+2y-1 can show one show me how to do this.

  • Math - ,

    First, 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 - ,

    i 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 - ,

    T.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.

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