1st you should find x in terms of y as x=g(y), then switch x & y positions and check domain and range values.
I got this from section 1.6 of James Stewart's 7th edition of Calculus
this one: http://www.amazon.com/Calculus-Trans.../dp/0538497904
the full question says
f(x)=3+x+e^x and then asks what f^-1(4) is
NOTE: by f^-1(4) I mean 'the inverse function of f at 4'