Question 252033
You have three denominators :m^2, n and m
Clearly m is a factor of m^2
so the common denominator will be nm^2
so multiply the fraction with m^2 as the denominator by n/n
the n denominator by m^2/m^2
the m denominator by mn/mn
The parts with no denominator by nm^2/nm^2
nm^4   +n^3  -m^2*n^4  +nm^3- nm^3+ m^2n^2+m^2n^2
now combine terms
nm^4-m^2n^4+n^3+2m^2n^2
All over nm^2