## Precalculus (6th Edition)

$-4$ is known to be a real number. RECALL: The number $a+bi$ where $a$ and $b$ are real numbers is a complex number. Since $-4= -4 + 0i$ and $-4 and 0$ are real numbers, then $-4$ is a complex number. Thus, $-4$ is: a real number; a complex number