Question

which numbers are complex? select all that apply -3i 3+2i √5 5 4i

Explanation:

All real numbers and imaginary numbers are part of the complex number system. A complex number is defined as $a+bi$ where $a$ (real part) and $b$ (imaginary part) are real numbers, and $i=\sqrt{-1}$.

• $-3i$ is $0 + (-3)i$ (complex, pure imaginary)
• $3+2i$ has both real and imaginary parts (complex)
• $\sqrt{5}$ is a real number, so it is ${\sqrt{5}}+0i$ (complex)
• $5$ is a real number, so it is $5+0i$ (complex)
• $4i$ is $0+4i$ (complex, pure imaginary)

Answer:

-3i, 3+2i, $\sqrt{5}$, 5, 4i