Chapter 5 - Exponents and Polynomials - 5.2 - Multiplying Monomials - Problem Set 5.2 - Page 200: 56

$-32a^3+72a^2+48a$

Using $a(b+c)=ab+ac$ (or the Distributive Property), the given expression, $ -8a(4a^2-9a-6) ,$ is equivalent to \begin{array}{l}\require{cancel} -8a(4a^2)-8a(-9a)-8a(-6) \\\\= -32a^3+72a^2+48a .\end{array}