Answer
$x^2-36.$
Work Step by Step
This is a product of the sum and difference of two terms, so we have
$$
(x-6)(x+6)=x^2-6^2=x^2-36.
$$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.