## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$\dfrac{6}{a^{4}b^{9}}$
Using the laws of exponents, the given expression, $(3a^{-5}b^{-7})(2ab^{-2})$, is equivalent to \begin{array}{l} 3(2)a^{-5+1}b^{-7+(-2)} \\\\= 6a^{-4}b^{-9} \\\\= \dfrac{6}{a^{4}b^{9}} .\end{array}