# Understand the Number i

##### This Understand the Number i video also includes:

Beginning with a question of when a square number is negative, this short but deep video presentation motivates the creation of the imaginary numbers. Common mistakes in developing the idea of i are carefully addressed, including confusion of the number with a variable and loss of negative signs when squaring. The emphasis on squares and square roots does a great job offering strong math justification for concepts that are often memorized without understanding.

CCSS: Designed

##### Instructional Ideas

• Create a memory-style game where learners match expressions and their verbal expansion, per time-stamp 3:45 on the video
• Link video on the class website for learners to use for on-demand review while working related homework problems
• Show during a comprehensive end-of-course review to refresh the theory behind imaginary numbers
##### Classroom Considerations

• Viewing the lesson requires creation of a free LearnZillion teacher account
• Video playing requires updated Adobe Flash player and Internet access
• Only pure imaginary numbers are covered, not complex numbers with both real and imaginary parts
• Lesson assumes learners are familiar with rational exponents and the Venn diagram representation of the real number systems and subsystems
• Printable note slides available under the Additional Materials tab
##### Pros

• Clear and easily understood narration, carefully matching text directions
• Identification and explanation of common areas of confusion
• Particular care taken with treatment and explanation of how to deal with negative numbers
##### Cons

• The imaginary number system is never called the more general and correct complex number system
• No workable problems or guided practice provided