已知单项式6x^m+1y^2m-3与2/3x^7-2my-1-2n的和是单项式,则2+mn=---

题目

已知单项式6x^m+1y^2m-3与2/3x^7-2my-1-2n的和是单项式,则2+mn=---

答案

∵单项式6x^m+1y^2m-3与2/3x^7-2my-1-2n的和是单项式
∴m+1=7-2m 2m-3=-1-2n
m=2 n=-1
2+mn=2+1*(-2)=2-2=0