Chapter 10 - Exponents and Radicals - 10.8 The Complex Numbers - 10.8 Exercise Set - Page 686: 48

$-20-24i$

Using $a(b+c)=ab+ac$, or the Distributive Property, and the properties of radicals, the given expression, $ -4i(6-5i) ,$ simplifies to \begin{array}{l}\require{cancel} -4i(6)-4i(-5i) \\\\= -24i+20i^2 \\\\= -24i+20(-1) \\\\= -24i-20 \\\\= -20-24i .\end{array}