y=1/3x²-1/2x-2a=1/3 ,b=-1/2 ,c=-2,对称轴为x=-b/(2a)；顶点坐标为[ -b/(2a),(4ac-b²)/(4a) ]x=-b/(2a)=(1/2)/(2×1/3)=3/4 对称轴为 x=3/4(4ac-b²)/(4a)=[4×1/3×(-2)-(-1/2)²]/(4×1/3)=(-8...