Task 6.8.1.c.ii.
It is true that \((z - r)^2 \geq (z - 2r)^2 - r^2\text{.}\) Assuming this, show that
\begin{equation*}
rx^2 + y^2 + b(z - r)^2 \geq mV - br^2,
\end{equation*}
where \(m\) is the smallest of the three numbers 1, \(1/a\text{,}\) and \(b/2a\text{.}\)