## Intermediate Algebra (6th Edition)

$z^{21}$
We are given the expression $(z^{3})^{7}$. To simplify, we can use the power rule, which holds that $(a^{m})^{n}=a^{m\times n}$ (where a is a real number, and m and n are integers). $(z^{3})^{7}=z^{3\times7}=z^{21}$