Another way to create new functions is by combining several functions. We
can add, subtract, multiply and divide functions to create new ones. The
thing to watch out for is the domains. A more complicated combination of
functions is called composition. This is where we take one function and
substitute it in as the variable in another function. Thus, if f and g
are functions, we could create a new function with values f(g(x)) by
composing them. Try a simple example. Let 
and g(x) = 2x
- 1. Then, 
. Here it is very important to get
the domain correct.