Question

已知,X+Y=6,XY=-3.则X的平方Y＋XY的三次方等于多少?

Answer 1

X+Y=6,XY=-3 x^2*y+x*y^3=xy(x+y^2)=-3(x+y^2) x=6-y,(6-y)y=-3,y^2-6y-3=0 (y-3)^2=3+9=12,y=3+2根号(3)或3-2根号(3) x^2*y+x*y^3=xy(x+y^2)=-3(x+y^2)分别代入即可!