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# Addition & Subtraction of Complex Numbers(With Examples)

August 20, 2022

This post is also available in: हिन्दी (Hindi)

A complex number is the combination of a real number and an imaginary number. It is of the form $a + ib$ and is usually represented by $z$. While adding two or more complex numbers, the real and imaginary parts of a complex number are added individually. Similarly, for the subtraction of complex numbers, the real and imaginary parts are subtracted separately.

While adding two or more complex numbers, you add real parts of complex numbers separately and similarly add imaginary parts of complex numbers separately.

The formula used to add two complex numbers $z_{1} = a + ib$ and $z_{2} = c + id$ is

$z_{1} + z_{2} = \left(a + ib \right) + \left(c + id \right) = \left(a + c \right) + \left(ib + id \right) = \left(a + c \right) + i \left(b + d \right)$.

Hence we have $\left(a + ib \right) + \left(c + id \right) = \left(a + c \right) + i\left(b + d \right)$.

### Steps for Adding Complex Numbers

Given below are the steps for adding complex numbers:

Step 1: Segregate the real and imaginary parts of the complex numbers

Step 2: Add the real parts of the complex numbers

Step 3: Add the imaginary parts of the complex numbers

Step 4: Write the final answer in $a + ib$ format

### Examples

Let’s consider some examples to understand the process of the addition of complex numbers.

Ex 1: Add $2 + 3i$ and $5 + 4i$.

Here, $z_{1} = 2 + 3i$ and $z_{2} = 5 + 4i$

The real parts of the two complex numbers are $2$ and $5$ and the imaginary parts of the two complex numbers are $3i$ and $i$.

On adding real parts we get $2 + 5 = 7$ and on adding the imaginary parts we get $3i + 4i = 7i$.

Therefore, $\left(2 + 3i \right) + \left(5 + 4i \right) = 7 + 7i$.

Ex 2: Add $4 + 9i$ and $2 + 3i$.

The two complex numbers are $z_{1} = a + ib = 4 + 9i$ and $z_{2} = c + id = 2 + 3i$.

So, $a = 4$, $b = 9$, $c = 2$, and $d = 3$

According to the formula, $\left(a + ib \right) + \left(c + id \right) = \left(a + c \right) + i\left(b + d \right)$

Therefore, $\left(4 + 9i \right) + \left(2 + 3i \right) = \left(4 + 2 \right) + i \left(9 + 3 \right) = 6 + 12i$.

Ex 3: Add $-2 + 7i$ and $6 – 5i$.

$\left(-2 + 7i \right) + \left(6 – 5i \right) = \left(-2 + 6 \right) + \left(7 + \left(-5 \right) \right)i = 4 + 2i$.

Maths can be really interesting for kids

### Properties of Addition of Complex Numbers

Following are the properties of the addition of complex numbers:

• Closure Property: The sum of complex numbers is also a complex number. Hence, it holds the closure property.
• Commutative Property: The addition of complex numbers is commutative.
• Associative Property: The addition of complex numbers is associative.
• Additive Identity: $0$ is the additive identity of the complex numbers, i.e., for a complex number $z$, we have $z + 0 = 0 + z = z$.
• Additive Inverse: For a complex number $z$, the additive inverse in complex numbers is $-z$, i.e., $z + \left(-z \right) = 0$.

## Subtraction of Complex Numbers

While subtracting two or more complex numbers, you subtract real parts of complex numbers separately and similarly subtract imaginary parts of complex numbers separately.

The formula used to subtract two complex numbers $z_{1} = a + ib$ and $z_{2} = c + id$ is