Explanation:
(A) To find inverse of f(x) = y = 1 / x - 3 :
Transform in terms of x
y = 1 / x - 3
x - 3 = 1 / y
x = 3 + 1 / y
Exchange x with y :

Therefore, g(x) is not inverse of f(x) and vice versa.
(B)
Domain of f(x) = R - {3}
Domain of g(x) = R - {0}