Question

A=2pi*r^2+2pi*rh, solve for positive r
Please unlock my intuitions after I divided both sides of the equation by 2pi, and got this: hr+r^2=A/(2pi)

Thank you.

Answer 1

A=2pi*r^2+2pi*rh,
hr+r^2=A/(2pi) now use the quadratic formula here
r^2 +hr-A/(2pi)=0..a=1,b=h,c=A/2pi using only positive value
r=[-h+sqrt(h^2 -(4A/2pi))]/2 answer......