Khan Academy on a Stick
Imaginary and complex numbers
Understanding and solving equations with imaginary numbers.

Introduction to i and Imaginary Numbers
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Introduction to i and imaginary numbers

Calculating i Raised to Arbitrary Exponents
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Calculating i raised to arbitrarily high exponents

Imaginary Roots of Negative Numbers
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Imaginary Roots of Negative Numbers

i as the Principal Root of 1 (a little technical)
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i as the principal square root of 1
The imaginary unit i
This is where math starts to get really cool. It may seem strange to define a number whose square is negative one. Why do we do this? Because it fits a nice niche in the math ecosystem and can be used to solve problems in engineering and science (not to mention some of the coolest fractals are based on imaginary and complex numbers). The more you think about it, you might realize that all numbers, not just i, are very abstract.

Complex numbers
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Complex Numbers

Complex numbers (part 1)
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Introduction to complex numbers. Adding, subtracting and multiplying complex numbers.

Complex numbers (part 2)
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Dividing complex numbers. Complex conjugates.

Adding Complex Numbers
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Adding Complex Numbers

Subtracting Complex Numbers
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Subtracting Complex Numbers

Multiplying Complex Numbers
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Multiplying Complex Numbers

Dividing Complex Numbers
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Dividing Complex Numbers

Complex Conjugates Example
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Complex Conjugates

Example: Complex roots for a quadratic
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Complex Roots from the Quadratic Formula

Algebra II: Imaginary and Complex Numbers
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2326, mostly imaginary and complex numbers
Complex numbers
Let's start constructing numbers that have both a real and imaginary part. We'll call them complex. We can even plot them on the complex plane and use them to find the roots of ANY quadratic equation. The fun must not stop!