mx^2+2xy-x-(3x^2-2nxy+3y)
=mx^2+2xy-x-3x^2+2nxy-3y
=(m-3)x^2+(2+2n)xy-x-3y
因为不含二次项,则
m-3=0 2+2n=0
m=3 n=-1
n^m=（-1）^3=-1
哈哈,太简单啦,给分吧