若|m+1/3|+(n-1/2)^2=0,求多项式m^2+2m^3n+n^2-2m^2-2m^3n+3n^2的值

绝对值和平方都大于等于0相加等于0,若有一个大于0,则另一个小于0,不成立。所以两个都等于0所以m+1/3=0,n-1/2=0m=-1/3,n=1/2m^2+2m^3n+n^2-2m^2-2m^3n+3n^2=-m^2+4n^2=-1/9+1=8/9