7m^2n-3mn^2+5m^2n+2mn^2\(≧▽≦)/~

问题描述:

7m^2n-3mn^2+5m^2n+2mn^2
\(≧▽≦)/~

7m^2n-3mn^2+5m^2n+2mn^2
=(7+5)m^2n+(-3+2)mn^2
=12m^2n-mn^2