[tex]\bf ~~~~~~\textit{parabola vertex form}
\\\\
\begin{array}{llll}
\boxed{y=a(x- h)^2+ k}\\\\
x=a(y- k)^2+ h
\end{array}
\qquad\qquad
vertex~~(\stackrel{2}{ h},\stackrel{-4}{ k})\\\\
-------------------------------\\\\
\underline{y}=a(\underline{x}-2)^2-4
\\\\\\
\textit{we also know that }
\begin{cases}
y=-1\\
x=3
\end{cases}\implies \underline{-1}=a(\underline{3}-2)^2-4
\\\\\\
3=a(1)^2\implies 3=a[/tex]
