Rewriting a number using i

The video tutorial explains how to simplify the expression sqrt -75 by breaking it into a product of sqrt 75 and sqrt -1. The instructor demonstrates how to simplify each radical separately, identifying sqrt -1 as 'i' and simplifying sqrt 75 by factoring it into sqrt 25 and sqrt 3. The final expression is simplified to 5i sqrt 3, illustrating the use of imaginary numbers in simplifying radicals.

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