y=-x²+10x-17
=-(x²-10x+25-25)-17
=-(x-5)²+8
4确定正确么- -。确定0<=(x-5)²<=43<=x<=7 这里不应该是 0＜=x＜=7么？为什么是3x=0，(x-5)²=25, 行吗？0<=(x-5)²<=4-2<=x-5<=23<=x<=7