Question

Solve s=πr^2+πrl for l

Answer 1

Start with

$S = \pi r^2 + \pi r l$

Subtract $\pi r^2$ from both sides:

$S - \pi r^2=\pi r l$

Divide both sides by $\pi r$

$\dfrac{S-\pi r^2}{\pi r}=l$

And thus we solved the expression for l:

$l=\dfrac{S-\pi r^2}{\pi r}$