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

$x^{-21}$
Using the laws of exponents, we multiply the exponents in the given expression: $(x^3)^{-7}$ \begin{array}{l}\require{cancel} x^{3(-7)} \\\\= x^{-21} \\\\ =1/x^{21} \end{array}