# Chapter 5 - Exponents and Polynomials - Chapter 5 Review Problem Set - Page 231: 72

$-12b$

#### Work Step by Step

Using the laws of exponents, the given expression, $(4ab^{-1})(-3a^{-1}b^2) ,$ simplifies to \begin{array}{l}\require{cancel} 4(-3)a^{1+(-1)}b^{-1+2} \\\\= -12a^{1-1}b^{-1+2} \\\\= -12a^{0}b^{1} \\\\= -12(1)b \\\\= -12b .\end{array}

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