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

$i$
Using $i^2=-1$ and the laws of exponents, the given expression, $i^{9} ,$ is equivalent to \begin{array}{l}\require{cancel} i^{8}\cdot i \\\\= \left( i^2 \right)^{4}\cdot i \\\\= \left( -1 \right)^{4}\cdot i \\\\= 1\cdot i \\\\= i \end{array}