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)²+(xy-6)²=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)²-2xy
    （x+y)²-2xy=5²-2x6=25-12=13