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已知xy=4满足想x²y-xy²-x+y=56.求x²+y²的值
人气:480 ℃ 时间:2019-12-13 16:46:50
解答
x²y-xy²-x+y
=xy(x-y)-(x-y)
=(xy-1)(x-y)
=56 xy=4
x-y=56/3
x²+y²=(x-y)^2+2xy=56^2/9+8
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