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Prove that if $a$ is an integer and not a square number then $\sqrt{a}$ is irrational.

 

NOTES AND BACKGROUND
If you have seen a proof that the square root of 2 is irrational the interactivity Proof Sorter may help you to understand the proof better. You can look this proof up in textbooks written for students in their last year of school mathematics or first year of university mathematics.