The video tutorial discusses the challenges of using direct substitution in rational expressions when the denominator becomes zero. It explains the importance of factoring to resolve these issues and how it helps identify holes in graphs. The tutorial further explores graph behavior and limits at these holes, emphasizing the continuity from both sides. Finally, it demonstrates graphing the expression x-4 and verifying results using a calculator.

How can direct substitution be applied to find the value at the hole?

Describe how the graph of the function x - 4 behaves as discussed in the text.