若(x+y-5)²+(xy-6)²=0,则（x+y)²-2xy的值为?

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若(x+y-5)²+(xy-6)²=0,则（x+y)²-2xy的值为?
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若(x+y-5)²+(xy-6)²=0,则（x+y)²-2xy的值为?
若(x+y-5)²+(xy-6)²=0,则（x+y)²-2xy的值为?

若(x+y-5)²+(xy-6)²=0,则（x+y)²-2xy的值为?
因为(x+y-5)&sup2;+(xy-6)&sup2;=0
    所以x+y-5=0,xy-6=0
    所以x+y=5,xy=6
    把x+y=5,xy=6代入（x+y)&sup2;-2xy
    （x+y)&sup2;-2xy=5&sup2;-2x6=25-12=13