\begin{equation}x^{2}=4\end{equation}

\begin{equation}5x^{2}-20=0\end{equation}

\begin{equation}2x^{2}=18\end{equation}

\begin{equation}8(x-9)(x-3)=0\end{equation}

\begin{equation}\frac{1}{x+7}=\frac{x^{2}}{x^{2}-49}-(\frac{1}{x-7})\end{equation}

\begin{equation}\frac{1}{8} \times (x+7)(x-7)=0\end{equation}