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1.1 Proof

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Question 46

A security analyst is verifying a property of an encryption key generation algorithm. The analyst needs to prove the following statement:

'For every non-zero rational number α\alphaα and every irrational number β\betaβ, the result of the calculation 5αβ\frac{5\alpha}{\beta}β5α​ is always an irrational number.'

Identify the correct starting assumption for a proof by contradiction of this statement.

  • There exists a non-zero rational number α\alphaα and an irrational number β\betaβ such that 5αβ\frac{5\alpha}{\beta}β5α​ is rational.
  • For all non-zero rational numbers α\alphaα and all irrational numbers β\betaβ, the value 5αβ\frac{5\alpha}{\beta}β5α​ is rational.
  • There exists a non-zero rational number α\alphaα and an irrational number β\betaβ such that 5αβ\frac{5\alpha}{\beta}β5α​ is irrational.
  • For all non-zero rational numbers α\alphaα and all irrational numbers β\betaβ, the value 5αβ\frac{5\alpha}{\beta}β5α​ is irrational.
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1.1 Proof Questions

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