你这题目有问题!应该是m+n=4吧?
=[(n+1)^2+(m+1)^2]/(m+1)(n+1)
=（n^2+2n+1+m^2+2m+1）/(mn+m+n+1)
=[(m+n)^2-2mn+8+2]/(-7)
=(16+24+10)/(-7)
=-50/7