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March 27, 2017

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Can you pliz help me solve the following simultaneous equation 3x-y=2 and 3y+9x=4

  • Maths - ,

    3x-y=2 Multiplt it by 3
    9x-3y=6 Add to it the other eq.
    9x+3y=4 You get 18x=10 or x=5/9
    Substitute in any eq.
    3*5/9-y=2 or y=15/9-2=5/3 -2
    or y=(5-6)/2=-1/6.
    Check: 3*5/9-(-1/6)=2 or 5/3+1/6=2
    or (10+2)/6=2 ok.
    9*5/9-3*1/3=4 or 5-1=4 ok.

  • check answer - Maths - ,

    or ... using substitution

    from the 1st: y = 3x-2
    sub into the 2nd

    3(3x-2) + 9x = 4
    9x - 6 + 9x = 4
    18x = 10
    x = 5/9

    back into the 1st:
    y = 3(5/9) - 2
    = 5/3 - 2
    = -1/3

    in original:
    1st equation:
    LS = 3(5/9) - (-1/3) = 6/3 = 2 = RS
    2nd equation:
    LS= 3(-1/3) + 9(5/9) = -1 + 5 = 4 = RS

    So x = 5/9 and y = -1/3

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