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Math Help - Find x in quadratic when y=11

  1. #1
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    Find x in quadratic when y=11

    Hi

    I have a quadratic -5x^2 + 15x +1 = 0

    I can find x where y=0, (-54.1 or +24.1)

    But how do I find x when y = 11

    Factorising, completing the square and using the quadratic formula are
    all about finding x when y = 0. But what do you do when you want y=
    some other value?

    Angus
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  2. #2
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    -5x^2 + 15x + 1 = 11

    -5x^2 + 15x - 10 = 0

    x^2 - 3x + 2 = 0

    (x - 1)(x - 2) = 0

    x -1 = 0 or x - 2 = 0

    x = 1 or x = 2.
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  3. #3
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    Why didn't I think of that

    Many thanks.
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