Imaginary numbers come in handy to do many computations, especially something called simplification. Here are some “simple” examples of how to use imaginary numbers:

To simplify the square root (or sqrt) of -25:

To simplify 2i + 4i:

To simplify 21i - 5i:

To multiply and simplify (2i)(4i):

(2i)(4i) = (2 × 4)(ii) = (8)(i²) = (8)(-1) = -8