7m^2n-3mn^2+5m^2n+2mn^2
问题描述：
7m^2n-3mn^2+5m^2n+2mn^2
\(≧▽≦)/~
答
7m^2n-3mn^2+5m^2n+2mn^2
=（7+5）m^2n+（－3+2）mn^2
＝12m^2n-mn^2