yx²+yx+y=x²-x+1(y-1)x²+(y+1)²+(y-1)=0x是实数则方程有解所以△>=0所以(y+1)²-4(y-1)²>=0(y+1+2y-2)(y+1-2y+2)>=0(3y-1)(-y+3)>=0(3y-1)(y-3)<=01/3
