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1.1.4 Proof by contradiction (A-level only)

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Question 35

In the field of cryptography, certain protocols rely on the property that specific constants are not rational. Let S S\,S be a constant defined by the equation S2−13=0S^2 - 13 = 0S2−13=0. Given that S>0S > 0S>0, prove by contradiction that S S\,S is an irrational number.

(You may assume that if n2 n^2\,n2 is a multiple of 13, then n n\,n is also a multiple of 13 for any integer nnn.)

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1.1.4 Proof by contradiction (A-level only) Questions

  1. A Level
  2. /Maths
  3. /1.1.4 Proof by contradiction (A-level only)

107 exam-style questions on OCR A Level Maths 1.1.4 Proof by contradiction (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.

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