Chapter 5 - Section 5.2 - Multiplying Polynomials - Exercise Set - Page 359: 62

$x^2-4x-96$

Using $(a+b)(c+d)=ac+ad+bc+bd$ or the Distributive Property, the given expression, $ (x-12)(x+8) ,$ is equivalent to \begin{array}{l}\require{cancel} x(x)+x(8)-12(x)-12(8) \\\\= x^2+8x-12x-96 \\\\= x^2-4x-96 .\end{array}