[tex]\bf \qquad \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\ ({{ h}},{{ k}})\\\\
-------------------------------\\\\
(1,-1)\implies \begin{cases}
h=1\\
k=-1
\end{cases}\implies y=a(x-1)^2-1
\\\\\\
\textit{and if we assume \boxed{a=1} then}\implies y=(x-1)^2-1[/tex]
