a^3m=3
则a^2m=9的立方根
b^3n=2
b^n=2的立方根
(a^2m)^3+(b^n)^3 - a^2mb^n
=a^6m+b^3n - a^2mb^n
=(a^3m)^2+b^3n - a^2mb^n
=9+2-18的立方根
=11-18的立方根