已知xy=n 且1
已知xy=n 且1/x^2 + 1/y^2=n 则(x-y)^2=详细不走
1/x^2+1/y^2=[(x-y)^2+2xy]/(xy)^2 n=[(x-y)^2+2n]/n^2 (x-y)^2=n^3-2n
解:1/x²+1/y²=n xy=n y²+x²=nx²y²=n³ (x-y)²=x²+y²-2xy=n³-2n
答:解: 因为x^2+3xy+y^2=(x-y)^2+5xy x-y=-3,(x-y)^2=9,xy=9 所以x^2+3xy+y^2=(-3)^2+5*9=54详情>>
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