Hello,

Does anyone know how to rearrange the formula:

A= 2*pi*r*h + pi*r^2

Make r the subject, I have an answer, but it doesn't match others answers?

Many thanks

Complete the square on pi*r^2 + 2*pi*r*h:

pi(r^2 + 2rh)
pi(r^2 + 2rh + h^2) - pi*h^2

A - pi*h^2
----------- = r^2 + 2rh + h^2
pi

A - pi*h^2
----------- = (r + h)^2
pi

A- pi*h^2
sqrt.---------- = r + h
pi

A - pi*h^2
sqrt. (------------) - h = r
pi