解(3x²+my-8)-(-nx²+2y+7)=(3x²+nx²)+(my-2y)+(-8-7)=(3+n)x²+(m-2)y-15∵与x,y的值无关∴m-2=0,3+n=0∴m=2,n=-3∴n^m+mn=(-3)²+2×(-3)=9-6=3