Hi my name is Cindy and I am new here and I need help on my math homework.

The first one says which of the following fuctions f(x) = sqrt 19 - x and g(x) = sqrt 25 - x^2 has an inverse. Find a rule for the inverse and explain why the other function has no inverse.

I don't understand inverses it would be nice if you could explain to me how you get the inverse.

Also I need help on this problem : Let f(x) = x^2, g(x) = x - 2 and h(x) = 4x, find the following:

A) f(g(h(x)) B) g(h(f(x))