Question

http://imgur.com/jgCnj

In the surface area formulas above, I understand that the f(x) will just be what f(x)/y equal (e.g. for y=x+4, f(x) in that formula will be x+4) but I do not understand what h(y) will be. Will it just be f(x) in terms of y? (e.g. for y = x+4, h(y) = y-4)

Answer 1

For example -- F[x]=y=x^2 ----> H[y]=x=Sqrt[y]
Just changing variable

Answer 2

Ok thats what I though, thanks