Final answer:
The classmate's answer is incorrect because x² + 36 cannot be factored using the difference of two squares.
Step-by-step explanation:
Your classmate's answer is not correct because the expression x² + 36 cannot be factored using the difference of two squares. The difference of two squares is a factoring method used when we have an expression of the form a² - b². In this case, we have x² + 36, which does not fit the pattern of a difference of two squares.
The correct way to factor x² + 36 would be to recognize that it is a sum of two squares and cannot be further factored. So the expression remains as x² + 36.