Solve l=sqrt{P/R}

$$l = \sqrt{ \frac{ P }{ R } }$$

Solve for P

$$P=Rl^{2}$$

$$l\geq 0\text{ and }R\neq 0$$

Steps for Solving Radical Equations

Swap sides so that all variable terms are on the left hand side.

$$\sqrt{\frac{P}{R}}=l$$

Square both sides of the equation.

$$\frac{1}{R}P=l^{2}$$

Divide both sides by R^{-1}.

$$\frac{\frac{1}{R}PR}{1}=\frac{l^{2}R}{1}$$

Dividing by R^{-1} undoes the multiplication by R^{-1}.

$$P=\frac{l^{2}R}{1}$$

Divide l^{2} by R^{-1}.

$$P=Rl^{2}$$

Solve for R

$$\left\{\begin{matrix}R=\frac{P}{l^{2}}\text{, }&l>0\text{ and }P\neq 0\\R\neq 0\text{, }&P=0\text{ and }l=0\end{matrix}\right.$$