Example 5: Domain
So:
Pay attention to domain of inside function
Inside function has to be in the domain of outside function
Let 𝑓𝑥=𝑥 and let 𝑔𝑥=𝑥2−4.
Find an expression for 𝑓∘𝑔𝑥 
Find the domain of 𝑓∘𝑔𝑥
Find an expression for 𝑔∘𝑓𝑥 
Find the domain of 𝑔∘𝑓𝑥