plumiProof by contradiction: WJEC A‑Level Maths questions
WJEC A-Level Maths past-paper questions on 1.3 Proof by contradiction, 2018–2025, with mark schemes and examiner’s reports where available. Add MadAsMaths questions to your practice, or browse them separately by topic and difficulty.
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All 4 questions on Proof by contradiction, as a list
- Summer 2025, Unit 3, Q9 (4 marks): Use proof by contradiction to show that there are no integers x and y for which 3 x 15 y 2 9. . [4]
- Summer 2024, Unit 3, Q5 (4 marks): 5. Prove by contradiction the following proposition: 81 18 When x is real and positive, x . [4] x x
- Summer 2019, Unit 3, Q15 (5 marks): 1 5 Use proof by contradiction to show that is irrational. [5]
- Summer 2018, Unit 3, Q11 (4 marks): π 1 1 Prove by contradiction that, for every real number x such that 0 X x X , 2 sinx + cosx x 1. [4]
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