Chapter 2 - Linear and Quadratic Functions - Section 2.7 Complex Zeros of a Quadratic Function* - 2.7 Assess Your Understanding - Page 177: 5

$\text{True}$

All real numbers are complex numbers as real numbers will not have an imaginary part but complex numbers have an imaginary part and a real part, so real numbers fall under the set of complex numbers. In $a+ib$, $a$ is the real number part while $b$ is the imaginary part . For real numbers, the imaginary part is $0$. Hence, all real numbers are complex numbers.