How to multiply two functions and identify domain

The video tutorial explains the multiplication of functions, specifically f(g(x)) as f(x) times g(x). It defines f(x) as 2x and g(x) as the square root of x minus 1. The tutorial discusses the challenges in simplifying the product and focuses on finding the domain by identifying restrictions, particularly when a variable is under a radical. The domain is determined by setting the radicand greater than or equal to zero.

How do you set the radicand to find the domain when it is under a radical?

What is the final domain for the function discussed in the text?