1/m + 1/n = 1/(m+n)易知m,n,(m+n)≠0,原等式两边同乘(mn),得：n+m=(mn)/(m+n)所以：mn=(m+n)²mn=n²+2mn+m²n²+mn+m²=0n²+m²=-mn(n²+m²)/(mn) = -1而：n/m + m/n=(n
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