|M+1/3|+（N-1/2）²=0,
|M+1/3|=0,（N-1/2）²=0,
M=-1/3
N=1/2
M²+2M^3N+2M²-2M^3N+3N²
=M²+2M²+2M^3N-2M^3N+3N²
=3M²+3N²
=3*(-1/3)²+3*(1/2)²
=1/3+3/4
=4/12+9/12
=13/12