将二次函数y=-2x的平方+5x+8和y=-3x的平方+8x-2化为顶点式

y=-2x²+5x+8
=-2(x²+5x/2)+8
=-2(x²+5x/2+25/16)+8+25/8
=-2(x+5/4)²+89/8
y=-3x²+8x-2
=-3(x²+8x/3)-2
=-3(x²+8x/3+16/9)-2+16/3
=-3(x+4/3)²+10/3