Introductory Algebra for College Students (7th Edition)

$5x^3+30x^2$
Using $a(b+c)=ab+ac$ or the Distributive Property, the given expression, $5x^2(x+6) ,$ is equivalent to \begin{array}{l}\require{cancel} 5x^2(x)+5x^2(6) \\\\= 5x^3+30x^2 .\end{array}