---
title: Complex Numbers Introduction
---
## Complex Numbers Introduction

A complex number is any number that can be expressed in the form of z = a + ib.

![i](https://www.codeproject.com/KB/cpp/882975/SquareRoot1.png)

 a is called the real part of the complex number, and b is called the imaginary part. 

#### Note
A pure imaginary number or a pure real number is also a complex number.

#### Examples
1. What is the real part of 2i+1?
A. Real part : 1

2. What is the imaginary part of 2 - 4i?
A. Imaginary part : -4

3. Is it a complex number z = 2i?
A. Yes , because we can write this number as z = 0 + 2i.

4. Is it a complex number z = 4?
A. Yes , because we can write this number as z = 4 + 0i.

#### More Information:
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- [Wikipedia : Complex Numbers](https://en.wikipedia.org/wiki/Complex_number)
- [More Information](https://www.khanacademy.org/math/algebra2/introduction-to-complex-numbers-algebra-2/the-complex-numbers-algebra-2/a/intro-to-complex-numbers)