Chapter 5 - Exponents and Polynomials - 5.3 - Multiplying Polynomials - Problem Set 5.3 - Page 207: 15

$x^2-6x-7$

Using the Distributive Property and then combining similar terms, the given expression, $ (x-7)(x+1) , $ is equivalent to \begin{array}{l}\require{cancel} x(x)+x(1)-7(x)-7(1) \\\\= x^2+x-7x-7 \\\\= x^2-6x-7 .\end{array}