a cheap way to do it will be
[tex] \bf \cfrac{L+1.25S^{\frac{1}{2}}-9.8D^{\frac{1}{3}}}{0.686}\implies \sqrt{\left( \cfrac{L+1.25S^{\frac{1}{2}}-9.8D^{\frac{1}{3}}}{0.686}\right)^2}
\\\\\\
\sqrt[3]{\left( \cfrac{L+1.25S^{\frac{1}{2}}-9.8D^{\frac{1}{3}}}{0.686}\right)^3}\implies \sqrt[4]{\left( \cfrac{L+1.25S^{\frac{1}{2}}-9.8D^{\frac{1}{3}}}{0.686}\right)^4} [/tex]
