# Complex numbers

Learn about complex numbers and how to add, subtract, and multiply them. This will come in useful when working with polynomials.

This course contains 5 segments:

**What are the imaginary numbers?**

Learn about the imaginary unit i (which is the square root of -1) and about imaginary numbers like 3i (which is the square root of -9).

**What are the complex numbers?**

Learn about complex numbers (spoiler: they are numbers that consist of both real and imaginary parts).

**The complex plane**

Learn how we can visualize complex numbers in a plane. This can be seen as an expansion of the 1-dimensional real number line into a 2-dimensional plane!

**Adding and subtracting complex numbers**

Learn how to add or subtract complex numbers. For example, write (2+3i)-(1+2i) as (1+i).

**Multiplying complex numbers**

Learn how to multiply complex numbers using the fact that i^2=-1 and the distributive property. For example, multiply (1+i) by (2+3i).

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Rating | Not enough ratings |
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Length | 5 segments |

Starts | On Demand (Start anytime) |

Cost | Free |

From | Khan Academy |

Download Videos | On all desktop and mobile devices |

Language | English |

Subjects | Mathematics |

Tags | Math Algebra II |

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Rating | Not enough ratings |
---|---|

Length | 5 segments |

Starts | On Demand (Start anytime) |

Cost | Free |

From | Khan Academy |

Download Videos | On all desktop and mobile devices |

Language | English |

Subjects | Mathematics |

Tags | Math Algebra II |

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