# Imaginary Numbers

Students learn that the imaginary number "i" is equal to the square root of –1, which means that i^2 is equal to (the square root of –1) squared, which equals –1. Students also learn to simplify imaginary numbers. For example, to simplify the square root of –81, think of it as the square root of –1 times the square root of 81, which simplifies to i times 9, or 9i. To simplify 11/8i, the first step is to get rid of the "i" in the denominator by multiplying both the numerator and the denominator of the fraction by i, to get 11i/8i^2, and remember that i^2 = -1, so we have 11i/8(-1), or 11i/-8, or –11i/8.
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