3x^2+my-8-(-nx^2+2y+7)
=3x^2+my-8+nx^2-2y-7
=3x^2+nx^2+my-2y-8-7
=(3+n)x^2+(m-2)y-15
不含有x,y項(xiàng)
即3+n=0,m-2=0
m=2
n=-3
n^m+mn
=(-3)^2+2*(-3)
=9-6
=3
你好,很高興為你解答,希望對(duì)你有所幫助,若滿意請(qǐng)采納.