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A student claims that \(\sqrt{2}+\sqrt{3}\) is a rational number. Which argument correctly identifies the error in the claim?

Answer and explanation

Correct answer: यदि \(\sqrt{2}+\sqrt{3}=r\), जहाँ \(r\) परिमेय है, तो \(\sqrt{3}=r-\sqrt{2}\) होगा; इसलिए \(\sqrt{3}\) परिमेय है।

Assume \(\sqrt{2}+\sqrt{3}=r\), with \(r\) rational. Option A is not a valid conclusion because rational minus irrational can still be irrational. Squaring gives \(r^2=5+2\sqrt{6}\), so \(\sqrt{6}=(r^2-5)/2\) would be rational, a contradiction. Exam tip: square a sum of surds to isolate the remaining radical.

Related tags

Number SystemsIrrational NumbersSurdsProof By ContradictionSquare RootsMisconception AnalysisProof Of Irrationality Of Square Root 2 And Square Root 3Mathematics

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