(x^2m)^3+(y^n)^3- x^2m*y^n
=x^6m+y^3n - (x^m)^2 *y^n
显然
x^6m=(x^3m)^2=4^2=16
y^3n=5
而(x^m)^2 *y^n= (³√4)^2 * ³√5=³√80=2 ³√10
故
(x^2m)^3+(y^n)^3- x^2m*y^n
=x^6m+y^3n - (x^m)^2 *y^n
=16+5 - 2 ³√10
=21 - 2 ³√10