OCR A Level Maths: Pure

Revision Notes

1.2.1 Proof by Contradiction

Proof by Contradiction

What is proof by contradiction?

  • A proof by contradiction assumes the opposite result is true
  • Then, through a series of logical steps, shows that this cannot be so

How do I do proof by contradiction?

  • This type of proof often involves explanation in words alongside mathematical statements
  • Start with a statement assuming the opposite is true
    • e.g. 'Assume...'

1.1.5 Proof by Contradiction Notes Diagram 1, Edexcel A Level Maths: Pure revision notes

  • Use prime factorisation to write a composite number as a product of primes

 

Proof by Contradiction Notes Diagram 2, A Level & AS Level Pure Maths Revision Notes

 

Worked example

Proof by Contradiction Example, A Level & AS Level Pure Maths Revision Notes

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Paul

Author: Paul

Paul has taught mathematics for 20 years and has been an examiner for Edexcel for over a decade. GCSE, A level, pure, mechanics, statistics, discrete – if it’s in a Maths exam, Paul will know about it. Paul is a passionate fan of clear and colourful notes with fascinating diagrams – one of the many reasons he is excited to be a member of the SME team.