Logic & Proof

Topic overview

Reasoning and counterexamples based on the given conditions, without treating additional advanced proof techniques as a prior requirement.

Discontinued; only retained for training on the final historical syllabus scope, and is not a current entrance examination.

Key points

◆Follow the prerequisite knowledge requirements given by the examination body; new concepts may only be used when the question provides sufficient guidance.
◆The examples on this site are training with a limited scope and do not represent full syllabus coverage or official difficulty.

Try each example yourself before checking the explanation.

1Basic examples within scope

Which of the following is a counter-example to the claim: "For all integers $n>0$ , $n^2+n+41$ is prime"?

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