[Math] How to prove if a sum of two specific irrational numbers is irrational

discrete mathematicsirrational-numbers

Prove that $\sqrt 2 + \sqrt 6$ is irrational. (Note that, in general, the sum of two irrational numbers could be rational.)

I tried attempting to use proof by contradiction but I'm unsure of how to go from even there. I have no clue other than that. Please help.

Best Answer

If it is rational, its square is also rational. But this would imply that $\sqrt{3}$ is rational.

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