已知(x+my)(x+ny)=x2+2xy-8y2,求m2n+mn2的值.
问题描述:
已知(x+my)(x+ny)=x2+2xy-8y2,求m2n+mn2的值.
答
∵(x+my)(x+ny)=x2+2xy-8y2,
∴x2+nxy+mxy+mny2=x2+(m+n)xy+mny2=x2+2xy-8y2,
∴m+n=2,mn=-8,
∴m2n+mn2=mn(m+n)=-8×2=-16.