【Rainbow Doll】評論
X2-3X+4<4X=0, X2-3X+4=4 X=1, X2-3X+4<4 (v)X=2, X2-3X+4<4 (v)X=3, X2-3X+4=4X=4, X2-3X+44X=-1, X2-3X+44所以只有兩個滿足條件