#### Answer

$a=-\frac{1}{2}$ and so the parabola opens left
$h=4$ and $k=0$ and so the vertex is $(4,0)$. Since the parabola opens left, the axis of symmetry is $y=0$.

#### Work Step by Step

$x=-\frac{1}{2}y^2+4$
$a=-\frac{1}{2}$ and so the parabola opens left
$h=4$ and $k=0$ and so the vertex is $(4,0)$. Since the parabola opens left, the axis of symmetry is $y=0$.