(a)[3]
Write $1-6x-x^2$ in the form $a-(x+b)^2$, with $a$ and $b$ as constants.
(b)[3]
The graph of $y=x^2$ is changed into the graph of $y=1-6x-x^2$ by a reflection and then a translation of $\begin{pmatrix} m \\ n \end{pmatrix}$. State the reflection and determine $m$ and $n$.