Imaginary Numbers Are Real (Part 2: A Little History)

In some cases, a square root of a negative number must exist in order to determine the roots of a cubic equation. An educational presentation provides a specific example of a cubic with a known root to have an understanding of a square root of a negative number.

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CCSS: Adaptable
Instructional Ideas

  • Have the class use del Ferro's formula presented in the video to confirm roots of cubic functions
  • Research Cardan's formula for cubic equations that include the x squared term and confirm that it works for cubics with real roots
Classroom Considerations

  • Second video in a nine-part series

  • Provides a historical view of why being able to take a square root of a negative number was necessary
  • Continues the progression of the history of complex numbers from the first video

  • None
Common Core