Chapter 6 - Section 6.2 - Factoring Trinomials Whose Leading Coefficient is 1 - Exercise Set - Page 436: 32

$(x+1)(x-16)$

The given expression, $ r^2-15r-16 ,$ has $c= -16 $ and $b= -15 .$ The possible factors of $c$ are $ \{ 1,-16 \} ,\{ 2,-8 \} \{ 4,-4 \} \{ -1,16 \} ,\{ -2,8 \} $. Among these factors, the pair whose sum is equal to $b$ is $\{ 1,-16 \}.$ Hence, the factored form is \begin{array}{l}\require{cancel} (x+1)(x-16) .\end{array}