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Thread: simultaneous equation

  1. June 1st 2009, 05:50 PM #1
    johnsy123
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    simultaneous equation

    could you please help me solve this simultaneous equation

    -3x+y=15<br /> x=2-2y
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  2. June 1st 2009, 07:09 PM #2
    TheEmptySet
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    Quote Originally Posted by johnsy123 View Post
    could you please help me solve this simultaneous equation

    -3x+y=15<br /> x=2-2y

    Just FYI Tex editor's don't recognize white space inside math tags so that is really hard to understand.

    -3x+y=15
    x=2-2y

    subbing the 2nd equation into the first gives

    -3(2-2y)+y=15 \iff -6+6y+y=15 \iff 7y=21 \iff y =3

    Now sub in to find x x=2-2(3)=-4 so the solution is

    (-4,3)
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