已知x+y=2,xy=-5求(1)1/x+1/y的值 (2)求1/x²+1/y²的值

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已知x+y=2,xy=-5求(1)1/x+1/y的值 (2)求1/x²+1/y²的值

已知x+y=2,xy=-5
(1)1/x+1/y=[xy(1/x+1/y)/(xy)=(x+y)/(xy)=-2/5
(2)1/x²+1/y²=[x²y²(1/x²+1/y²)/(x²y²)=(y²+x²)/(xy)²=[(x+y)²-2xy]/(xy)²=14/25
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已知x+y=2,xy=-5求
(1)1/x+1/y的值
=(x+y)/(xy)
=2/(-5)
=-2/5;
(2)求1/x²+1/y²的值
=(x²+y²)/(x²y²)
=[(x+y)²-2xy]/(x²y²)
=[2²+10]/25
=14/25;
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