Solving (a)
The two functions we have are:

We are asked to find the composite function:

Step 1. The definition of a composite function is:

In this case:

This means to plug the g(x) expression into the value of x of the f(x) function.
Step 2. Substituitng g(x) as the value for x in f(x):

Simplifying:

Step 3. We also need to find the domain of this composite function.
The domain of a function is the possible values that the x-variable can take. In this case, there would be no issues with any x value that we plug as the x-value. Therefore, the domain is all real numbers.
The domain of fog is all real numbers.
Answer:

The domain of fog is all real numbers.