已知4x^2+y^2-4x+2y+2=0,则xy=?
问题描述:
已知4x^2+y^2-4x+2y+2=0,则xy=?
答
4x²+y²-4x+2y+2
=(2x-1)²+(y+1)²
=0
2x-1=0 y+1=0
x=1/2 y=-1
xy=1/2*(-1)=-2分之1