Multiplying Complex Numbers

In the last unit, we learned to simplify complex numbers by combining like terms. We learned variable "i" can be temporarily replaced by "x" to make the solution easier for you.

Now that you've had some experience adding and subtracting complex numbers, next we will multiply complex numbers.

To multiply complex numbers you use the Distributive Property or FOIL. While it is still okay to replace "i" with "x" during the Foil-ing, I would not recommend this. It will cause us to get the wrong answer because something tricky happens.

Let's go back and talk about the definition of "i" for a minute. √-1 = i. If we squared both sides of the equation, the value i² = -1. This is the tricky term that we will need to keep an eye out for when we are using FOIL to multiply the two binomials.

FOIL works the same way as always.

Multiplying (5 + 3x)(4 - 2x) is no different then multiplying (5 + 3i)(4 - 2i). Just keep an eye out for any i² terms in which we will use substitution since i² = -1.

Leaving i² in the answer will get marked as incorrect. Because i² can be simplified by substituting -1, you must do this step to get the correct answer. Don't forget the tricky term!

Multiplying Complex Numbers

In the last unit, we learned to simplify complex numbers by combining like terms. We learned variable "i" can be temporarily replaced by "x" to make the solution easier for you. Now that you've had some experience adding and subtracting complex numbers, next we will multiply complex numbers.

In the last unit, we learned to simplify complex numbers by combining like terms. We learned variable "i" can be temporarily replaced by "x" to make the solution easier for you.

Now that you've had some experience adding and subtracting complex numbers, next we will multiply complex numbers.