m+n=3,m-n=2,求m²+n²和mn的值

问题描述:

m+n=3,m-n=2,求m²+n²和mn的值

解析:已知m+n=3,m-n=2,那么:(m+n)²=m²+2mn+n²=9 (1)(m-n)²=m²-2mn+n²=4(2)(1)+(2)可得:2(m²+n²)=13解得m²+n²=13/2(1)-(2)可得:4mn=5解...