若m^2+n^2=10,m-n=2,则m+n=

问题描述:

若m^2+n^2=10,m-n=2,则m+n=

m^2 + ( m-2)^2 = 10
2m^2 - 4m + 4 = 10
m^2 - 2m -3=0
(m-3)(m+1)=0
因此.m=3 或 m=-1