Section 11.4 Complex Number Operations
Subsection 11.4.1 Adding and Subtracting Complex Numbers
Adding and subtracting complex numbers is just like combining like terms. We combine the terms that are real and the terms that are imaginary. Here are some examplesExample 11.4.1.
Simplify the expression
Example 11.4.2.
Simplify the expression
Checkpoint 11.4.3.
Subsection 11.4.2 Multiplying Complex Numbers
Now let's learn how to multiply complex numbers. It is very similar to multiplying polynomials, with the exception that must be replaced withExample 11.4.4.
Simplify the expression
We distribute the to both terms, then we simplify any powers of
Note that we always write a complex number in standard form, which is
Example 11.4.5.
Multiply
We will use the distributive method to multiply the two binomials.
Example 11.4.6.
Expand and simplify the expression
We will use the FOIL method to expand this perfect square.
Example 11.4.8.
Multiply
We will use the Generic Rectangle Method to multiply those two binomials.
Example 11.4.10.
Here is an example using the sum and difference formula to multiply
Checkpoint 11.4.11.
Subsection 11.4.3 Dividing Complex Numbers
When we divide by we use a process that is similar to rationalizing the denominator. We use the property when we rationalize the denominator, and we use the property when we have complex numbers. Let's compare these two problems andExample 11.4.12.
Rationalize the denominator in the expression
Checkpoint 11.4.13.
Example 11.4.14.
Simplify the expression
To get a real result in the denominator we multiply the numerator and denominator by \(4-3i\text{,}\) and we have:
Note that we always write complex numbers in standard form, which is \(a+bi\text{.}\)
Example 11.4.15.
Simplify the expression
To divide complex numbers, we rationalize the denominator using the conjugate \(2+4i\text{:}\)
Checkpoint 11.4.16.
Exercises 11.4.4 Exercises
Adding and Subtracting Complex Numbers
1.
Add up the following complex numbers:
2.
Add up the following complex numbers:
3.
Subtract the following complex numbers:
4.
Subtract the following complex numbers:
5.
Write the complex number in standard form.
6.
Write the complex number in standard form.
7.
Write the complex number in standard form.
8.
Write the complex number in standard form.
9.
Write the complex number in standard form.
10.
Write the complex number in standard form.
11.
Write the complex number in standard form.
12.
Write the complex number in standard form.
Multiplying Complex Numbers
13.
Multiply the following complex numbers:
14.
Multiply the following complex numbers:
15.
Multiply the following complex numbers:
16.
Multiply the following complex numbers:
17.
Multiply the following complex numbers:
18.
Multiply the following complex numbers:
19.
Multiply the following complex numbers:
20.
Multiply the following complex numbers:
21.
Write the complex number in standard form.
22.
Write the complex number in standard form.
23.
Write the complex number in standard form.
24.
Write the complex number in standard form.
Dividing Complex Numbers
25.
Rewrite the following expression into the form of a+b
26.
Rewrite the following expression into the form of a+b
27.
Rewrite the following expression into the form of a+b
28.
Rewrite the following expression into the form of a+b
29.
Rewrite the following expression into the form of a+b
30.
Rewrite the following expression into the form of a+b
31.
Write the complex number in standard form.
32.
Write the complex number in standard form.
33.
Write the complex number in standard form.
34.
Write the complex number in standard form.