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1.1.4 Proof by contradiction (A-level only)

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Question 47

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.

  • 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.
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1.1.4 Proof by contradiction (A-level only) Questions

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