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Math Help - The values of X and Y

  1. #1
    Junior Member Dragon's Avatar
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    The values of X and Y

    Find the values of x+y if x^2+y^2=36 and if xy=10.
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  2. #2
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by Dragon View Post
    Find the values of x+y if x^2+y^2=36 and if xy=10.
    xy = 10

    2xy = 20

    Thus
    x^2 + y^2 + 2xy = 36 + 20 = 56

    (x + y)^2 = 56

    x + y = (+/-)sqrt(56) = (+/-)sqrt(4*14) = (+/-)2*sqrt(14)

    -Dan
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  3. #3
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    Hello, Dragon!

    A different spin on Ron's solution . . .


    Find the values of x + y .if x + y = 36 and xy = 10

    Consider: .(x + y) .= .x + 2xy + y .= .(x + y) + 2(xy) .= .36 + 2(10)

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .__ . . . . . .__
    So we have: .(x + y) .= .56 . . x + y .= . √56 .= .2√14

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