y=-x^2+2x+3=-(x^2-2x+1)+4=-(x-1)^2+4

题目

y=-x^2+2x+3=-(x^2-2x+1)+4=-(x-1)^2+4
交点式化成顶点式
谁给我说说这怎么化的

答案

y=-x^2+2x+3
=-x^2+2x-1+4
=-(x^2-2x+1)+4
=-(x-1)^2+4
=2^2-(x-1)^2
=(2+(x-1))(2-(x-1))
=(1+x)(3-x)