recall that a square is just a rectangle with all sides equal.
and the area of a rectangle is just length * width.
[tex]\bf \textit{area of a rectangle}\\\\
A=length\cdot width\quad
\begin{cases}
length=x\\
width=x\\
A=112
\end{cases}\implies 112=x\cdot x\implies 112=x^2
\\\\\\
\sqrt{112}=x\implies \sqrt{16\cdot 7}=x\implies \sqrt{4^2\cdot 7}=x\implies 4\sqrt{7}=x[/tex]
