(m+n)²=5²m²+n²+2mn=25m²+n²=25-2mn=25+6=31所以原式=(m²+n²)/m²n²=(m²+n²)/(mn)²=31/9
1/㎡+1/n²=(m²+n²)/㎡n²=[(m+n)²-2mn]/(mn)²=(25+6)/9=31/9
1/㎡+1/n²=(n²+m²)/(mn)²n²+m²=(n+m)²-2mn=5²+6=31∴31/9
1/m²+1/n²=(m²+n²)/m²n²=[(m+n)²-2mn]/m²n²=(25+6)/9=31/9