m=2,n=-3,m-n=2-(-3)=5
mx²+2x-3=2x²+2x+n,袭嫌猜则拍型m-n=__5___(m-2)x²者碰-(3+n)=0m-2=0 x=0或3+n=0m=2 n=-32-(-3)=5
显然,左边与右边的每个项系数对应起来就行,即m=2,n=-3,所以m-n=5
mx²+2x-3=2x²+2x+n,则m-n=__5___
mx²-3=2x²+nmx²-n=2x²+3m=2,n=-3m-n=5