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.