已知x+y=10,xy=4,求x²+y²和(x-y)²的值
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![已知x+y=10,xy=4,求x²+y²和(x-y)²的值](/uploads/image/z/3169749-21-9.jpg?t=%E5%B7%B2%E7%9F%A5x%2By%3D10%2Cxy%3D4%2C%E6%B1%82x%26%23178%3B%2By%26%23178%3B%E5%92%8C%EF%BC%88x-y%EF%BC%89%26%23178%3B%E7%9A%84%E5%80%BC)
已知x+y=10,xy=4,求x²+y²和(x-y)²的值
已知x+y=10,xy=4,求x²+y²和(x-y)²的值
已知x+y=10,xy=4,求x²+y²和(x-y)²的值
x²+y²
=(x+y)²-2xy
=10²-2*4
=100-8
=92
(x-y)²
=(x+y)²-4xy
=10²-4*4
=100-16
=84
x²+y²=﹙x+y﹚²-2xy=10²-8=92
﹙x-y﹚²=﹙x+y﹚²-4xy=10²-4×4=84