Solve r:S=4pir^2

$$r : S = 4 \pi r ^ { 2 }$$

Solve for S

$$\left\{\begin{matrix}S=\frac{1}{4\pi r}\text{, }&r\neq 0\\S\neq 0\text{, }&r=0\end{matrix}\right.$$

Steps for Solving Linear Equation

Variable S cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by S.

$$r=4\pi r^{2}S$$

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

$$4\pi r^{2}S=r$$

Divide both sides by 4\pi r^{2}.

$$\frac{4\pi r^{2}S}{4\pi r^{2}}=\frac{r}{4\pi r^{2}}$$

Dividing by 4\pi r^{2} undoes the multiplication by 4\pi r^{2}.

$$S=\frac{r}{4\pi r^{2}}$$

Divide r by 4\pi r^{2}.

$$S=\frac{1}{4\pi r}$$

Variable S cannot be equal to 0.

$$S=\frac{1}{4\pi r}\text{, }S\neq 0$$

Solve for r

$$r=\frac{1}{4\pi S}$$

$$r=0\text{, }S\neq 0$$