若9m2+4n2-6m+4n+2=0求m+n的值
9m2+4n2-6m+4n+2
=（3m-1)^2+(2n+1)^2
>=0
因为9m2+4n2-6m+4n+2=0
所以3m-1=0,2n+1=0
得m=1/3,n=-1/2
m+n=-1/6