<s>[INST] Simple algebra simplification I have 
$ \frac{-8rS^{2} \pm \sqrt{64r^{2}S^{4} + 4}}{2}$
Which simplified to 
$ -4rS^{2} \pm \sqrt{16r^{2}S^{4} +1}$
But I can’t seem to get this
 [/INST] Let $$D = \frac{-8rS^{2} \pm \sqrt{64r^{2}S^{4} + 4}}{2}$$
Now
\begin{align}
D &= \frac{-8rS^{2} \pm \sqrt{64r^{2}S^{4} + 4}}{2}\\
&=\frac{-8rS^{2}}{2} \pm \frac{\sqrt{64r^{2}S^{4} + 4}}{2} \\
&= -4rS^2 \pm \frac{\sqrt{64r^{2}S^{4} + 4}}{\sqrt{4}} \\
&= -4rS^2 \pm \sqrt{\frac{64r^{2}S^{4} + 4}{4}}\\
&=-4rS^2 \pm \sqrt{16r^{2}S^{4} + 1}
\end{align}
</s>