The value of $$\frac{{\left\{ {\left( {{m^2} + {n^2}} \right)\left( {m - n} \right) - {{\left( {m - n} \right)}^3}} \right\}}}{{\left( {{m^2}n - m{n^2}} \right)}}$$      is:

$$\eqalign{ & \frac{{\left\{ {\left( {{m^2} + {n^2}} \right)\left( {m - n} \right) - {{\left( {m - n} \right)}^3}} \right\}}}{{\left( {{m^2}n - m{n^2}} \right)}} \cr & = \frac{{\left( {m - n} \right)\left[ {{m^2} + {n^2} - {{\left( {m - n} \right)}^2}} \right]}}{{mn\left( {m - n} \right)}} \cr & = \frac{{{m^2} + {n^2} - {m^2} - {n^2} + 2mn}}{{mn}} \cr & = \frac{{2mn}}{{mn}} \cr & = 2{\text{ Answer}} \cr} $$