你要先画出图像：开口向下,与Y轴交点为3,对称轴为K,若K2,则-4+4K+3=3,解得K=1,不满足,舍去,
若K属于[-1,2],则-K^2+2K^2+3=3,解得K^2=0,K=0,满足
综上所述,K=0