## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$(t^2+1)(t+1)(t-1)$
Using $x^2-y^2=(x+y)(x-y)$ or the factoring of the difference of 2 squares, then the factored form of the given expression, $t^4-1 ,$ is \begin{array}{l} (t^2+1)(t^2-1) \\\\= (t^2+1)(t+1)(t-1) \end{array}