+9466 Is this your question?
\(\sqrt{l(l-5)}=6\)
Square both sides of the equation.
\(\sqrt{l(l-5)}^2=6^2 \\~\\ l(l-5)=36\)
Distribute the l to both terms in parenthesees.
\(l^2-5l=36\)
Subtract 36 from both sides of the equation.
\(l^2-5l-36=0\)
Use the quadratic formula to solve for l .
\(l=\frac{-(-5)\pm\sqrt{(-5)^2-4(1)(-36)}}{2(1)} \\~\\ l=\frac{5\pm\sqrt{25+144}}{2} \\~\\ l=\frac{5\pm13}{2} \\~\\ \begin{array} \ l=\frac{5+13}{2}\qquad &\text{or}&\qquad l=\frac{5-13}{2}\\~\\ l=9&\text{or}&\qquad l=-4 \end{array}\)
