# Chapter 8 - Complex Numbers, Polar Equations, and Parametric Equations - Section 8.1 Complex Numbers - 8.1 Exercises - Page 357: 9

complex, pure imaginary, non-real complex

#### Work Step by Step

If $a$ and $b$ are real numbers, then any number of the form $a+bi$ is a complex number. Since $a=0$ and $b=13$ and both $a$ and $b$ are real numbers, $13i$ is a complex number. For a complex number $a+bi$, if $a=0$ and $b\ne0$, then the complex number is said to be a pure imaginary number. Since $13i$ fits this criteria, it is a pure imaginary number. Since pure imaginary numbers are a subset of the set of non-real complex numbers, $13i$ is a non-real complex number as well.

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