1.4.2b Finding a new function given a composite function (Case B : Second function is given) Example 2

Example 2 (Substitution Method)
A function f is defined by

f : x \mapsto x - 1

.
Find the function g if

g f : x \mapsto \frac{4}{x + 2}, x \neq - 2

.

[Note : Second function is given , use substitution y = x – 1]