Answer
$y=-\frac{3}{16}\cdot(x-4)^2+7$
Work Step by Step
The vertex form of the parabola is $y=a(x-4)^2+7$ and if $x=0, y=0$, so
$$
\begin{aligned}
4 & =a(0-4)^2+7 \\
-3 & =16 a \\
-\frac{3}{16} & =a
\end{aligned}
$$ Hence $$y=-\frac{3}{16}\cdot(x-4)^2+7.$$
