Evaluating functions with a binomial

The video tutorial explains how to evaluate a function R at a given expression X+2. It starts by defining the function R with a rule of 1 + 3X. The tutorial then demonstrates how to substitute the expression X+2 into the function, apply the distributive property, and combine like terms to simplify the expression. The final result shows that the value of the function R at X+2 is equal to 3X + 7.

Explain why X + 2 is considered an expression rather than a definitive value.

What is the final expression for the function R after combining like terms?