Imaginary numbers can be a source of confusion when they are first introduced to a student, but they don’t have to be. Basically, we are trying to deal with the problem of the square root of a negative number. When we take the square root of negative one, the number is called** i.**

This video lesson includes a brief explanation of complex numbers and a tutorial on how to use your TI-84+ to do calculations involving complex numbers. It covers square roots of negative numbers, multiplying complex numbers, and rationalizing complex numbers. An 84 plus can make complex numbers simple, even easy, but you’ll want to follow along with the review of complex numbers by hand first.

Also, a warning for users of TI-84 OS 2.53. The new fraction features do not work well with the imaginary numbers. You can’t use the new fraction bar with a complex number. The workaround for this problem is covered in the video. It’s also not possible to convert complex decimals back to fractions using the normal “frac” feature in the math menu. This is a really unfortunate change since it was possible in earlier versions of the 84 OS. I am really hopeful Texas Instruments will correct this in a future release.

### Related articles:

- Video lesson: Imaginary and complex numbers on the TI-Nspire
- Video lesson: Solving polynomial equations on the TI-Nspire
- Video lesson: Solving polynomial equations on the TI-84

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