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A2 1 Pure Mathematics
Quick questions on Proof: deduction, exhaustion, counter-example and contradiction - CCEA A-Level Mathematics
5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is proof by contradiction?Show answer
A proof by contradiction assumes the negation of what you want to prove, then derives a logical impossibility. Since the reasoning is valid but the conclusion is absurd, the assumption must be false, so the original statement is true. The classic example is the irrationality of .
What is incomplete exhaustion?Show answer
Proof by exhaustion only works if your cases cover every possibility; missing a case breaks the proof.
What is q1?Show answer
Disprove: "all prime numbers are odd". [1 mark]
What is q2?Show answer
Prove that the product of two even numbers is divisible by . [3 marks]
What is q3?Show answer
What is the first step of a proof by contradiction? [1 mark]
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