The value of frac(m^2 +n^2)(m−n)(m−n)^3(m^2n−mn^2) is:

 $\frac{\{(m^2 +n^2)(m−n)(m−n)^3\}}{(m^2n−mn^2)}$

= Let the values of m = 2 and n = 1 and put it into the given equation,

=  $\frac{\{(2^2 +1^2)(2−1)(2−1)^3\}}{(2^21−2×1^2)}$

= $\frac{5}{2}$