**Intro to rationalizing the denominator | Algebra (video ...**
https://www.khanacademy.org/math/algebra-home/alg-exp-and-log/miscellaneous-radicals/v/how-to-rationalize-a-denominator

When we have a fraction with a root in the denominator, like 1/√2, it's often desirable to manipulate it so the denominator doesn't have roots. To do that, we can multiply both the numerator and the denominator by the same root, that will get rid of the root in the denominator. For example, we can multiply 1/√2 by √2/√2 to get √2/2

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