McGraw Hill Integrated II, 2012
MH
McGraw Hill Integrated II, 2012 View details
2. Complex Numbers
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Exercise 1 Page 182

The imaginary number i is a complex number whose square is - 1.

9i

Practice makes perfect
We want to simplify the given numeric expression using the imaginary number i. To do so, we will first recall that the imaginary unit i is the complex number whose square is - 1. i^2=- 1 and i=sqrt(- 1) We can simplify the expression using this definition.
sqrt(- 81)
sqrt(- 1* 81)
sqrt(- 1)* sqrt(81)
i* sqrt(81)
i* 9
9i