Chapter 5 - Polynomials and Factoring - 5.4 Factoring Perfect-Square Trinomials and Differences of Squares - 5.4 Exercise Set - Page 333: 79

$(t^2+1)(t+1)(t-1)$

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}