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Study Guides > Intermediate Algebra

Introduction: Complex Numbers

Up to now, you’ve known it was impossible to take a square root of a negative number. This is true, using only the real numbers. But here you will learn about a new kind of number that lets you work with square roots of negative numbers! Complex numbers are made from both real an imaginary numbers.  Imaginary numbers result from taking the square root of a negative number. We will first define and perform algebraic operations on complex numbers, then we will provide examples of quadratic equations that have solutions that are complex numbers.

In this lesson you will learn how to do the following:

  • Express roots of negative numbers in terms of i.
  • Express imaginary numbers as bi and complex numbers as [latex]a+bi[/latex].
  • Add complex numbers.
  • Subtract complex numbers
  • Multiply complex numbers.
  • Find conjugates of complex numbers.
  • Divide complex numbers.
  • Simplify powers of i

The learning activities for this lesson include:

  • Read: Imaginary and Complex Numbers
  • Self-Check: Imaginary and Complex Numbers
  • Read: Add and Subtract Complex Numbers
  • Self-Check: Add and Subtract Complex Numbers
  • Read: Multiply and Divide Complex Numbers
  • Self-Check: Multiply and Divide Complex Numbers