（1）y=-x²+2x+5 =-（x²-2x+1)+1+5=-(x-1)²+6对称轴是直线x=1,顶点坐标 (1,6)（2）y=1-4x-1/2x²=-1/2(x²+8x)+1=-1/2(x²+8x+16)+8+1=-1/2(x+4)²+9对称轴是直线x=-4,顶点坐标 (-4,...