Completing the Square

Consider the given equation. $$\begin{array}{c}{x}^2+10x=\text{-}20\end{array}$$ Let's start by solving it by completing the square. We see above that $b$ $=$ $10.$ Therefore, we need to start by adding ${\left(\frac{10}{2}\right)}^2$ $=$ $25$ to both sides. We found two solutions, $x=\text{-}5+\sqrt{5}$ and $x=\text{-}5-\sqrt{5}.$ Thus, we've showed that the equation can be solved by completing the square.