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1.1 Proof by Contradiction

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Question 19

Leo wishes to use proof by contradiction to prove the following statement:

'The sum of a rational number and an irrational number is always irrational.'

Identify the correct starting assumption for Leo's proof. Explain your choice.

  • The sum of every rational number and every irrational number is irrational.
  • The sum of every rational number and every irrational number is rational.
  • There exists a rational number and an irrational number whose sum is rational.
  • There exists a rational number and an irrational number whose sum is irrational.
[4]
Markscheme

1.1 Proof by Contradiction Questions

  1. A Level
  2. /Maths
  3. /1.1 Proof by Contradiction

107 exam-style questions on Edexcel A Level Maths 1.1 Proof by Contradiction. Each one has a worked solution and a mark scheme showing where the marks go.

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