Question

How to know if a square root is rational or irrational?

Answer 1

Hi!

If it can be written as a fraction, then it is rational. If it cannot, it is rational.

Here are some examples.

√4 = 2 = 2/1 = rational

√7 = 2.64575131... = irrational

Hope this helps! :)

-Peredhel

Answer 2

The square root of an integer is rational if the integer is a square. Otherwise, the root is irrational.

Example: √4 = √(2²) = 2, is rational. √3 is irrational.

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(It can be helpful to memorize the squares of small integers, up to about 20 or 25.)