Complex Numbers – Add, Subtract, Multiply, and Divide Addition of complex numbers is given by: Example 1:

It is good to leave out the middle step and to work the problem completely in your head. Example 2: It is perfectly fine to think of addition of complex numbers as adding binomials, but remember that i is not a variable, but an imaginary number.

Subtraction of complex numbers is given by: Example 3:

Again, not all the steps were necessary, and learning to work the problem quickly in your head is good. Example 4:

Multiplication of complex numbers is given by: It is often easier to think of multiplication of complex numbers using the foil pattern for binomials, even though these are numbers and not true binomials. Again, remember that i is not a variable, but an imaginary number

Example 5:

Example 6:

Consider the complex number The Complex Conjugate of this number is given by: Notice what happens when you multiply complex conjugates.

Notice the difference between multiplying complex conjugates and multiplying binomials as in previous work. Binomials Complex Conjugate When multiplying complex conjugates, remember the + sign!

Example 7: Complex Number Complex Conjugate

To compute the Division of complex numbers, multiply both the numerator and the denominator by the complex conjugate of the denominator.

Example 8:

The problem is not complete at this point The problem is not complete at this point. Always express complex number answers in a+bi form.

Example 9:

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