因为m^2=n+2,n^2=m+2 所以 m^2-n^2=（n+4）-(m+4)=n-m 即 (m-n)(m+n)=-(m-n) m+n=-1 m^3-2mn+n^3=m·m^2-2mn+n·n^2 =(n+2)m-2mn+(m+2)n=mn+2m-2mn+mn+2n=2(m+n)因为m+n=-1 所以m^3-2mn+n^3=-2