Answer
$(x^2+1)(x+1)(x-1)$
Work Step by Step
Using $a^2-b^2=(a+b)(a-b)$ or the factoring of the difference of 2 squares, then,
\begin{array}{l}
x^4-1
\\=
(x^2+1)(x^2-1)
\\=
(x^2+1)(x+1)(x-1)
.\end{array}
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.