抛物线y=ax²+bx+c的顶点坐标为[ -b/2a,(4ac-b²)/4a ]y=-1/2x²+2x+1 配方,配成顶点式=-1/2(x²-4x)+1=-1/2(x²-4x+4)+1+4×1/2=-1/2(x-2)²+3平移后抛物线的顶点坐标为(2,3)∵a=-1/2,把a=...