Chapter 5 - Section 5.2 - Multiplying Polynomials - Exercise Set - Page 359: 53

$12x^4-3x^3+15x^2$

Using $a(b+c)=ab+ac$ or the Distributive Property, the given expression, $ -3x^2(-4x^2+x-5) ,$ is equivalent to \begin{array}{l}\require{cancel} -3x^2(-4x^2)-3x^2(x)-3x^2(-5) \\\\= 12x^4-3x^3+15x^2 .\end{array}