I have the following problems to solve:

The temperature u(r) in the circular ring shown in the image is determined from the boundary-value problem

where u_{0}and u_{1}are constants. Show that Not sure where to start. I need to show and explain every step.

#2 is similar but is sphere with equation of

r(d^2u/dr^2) + 2(du/dr) = 0

u_{0}and u_{1}are constants

I know the answer is u(r) = ((u0-u1)/(b-a))*ab/r +(u1b-u0a)/(b-a)

not sure how to get here though.

Any help to start would be great.

Thanks