How to evaluate a function with an expression

The video tutorial explains how to work with linear functions by inputting expressions instead of numbers. It highlights the process of replacing X with an expression, applying the distributive property, and simplifying the result. The tutorial emphasizes that the method remains consistent, even when expressions are used as input values.

Explain the significance of the input value in the context of the function.

What steps are involved in simplifying the expression after substituting the input value?