Imaginary Numbers (Jump to: Lecture | Video )

Let’s say you have the following equation:

Figure 1.

How would we solve this equation for x? In order to solve for x, we need to take the square root of a negative number. Previously, we have been unable to do this. In order to make it work, we're going to create an Imaginary Number:

Imaginary Number

Pure Imaginary Numbers
Pure Imaginary Numbers are the square roots of negative real numbers, such as:

Here's how you would take the square root of -45:

Figure 2.