Practice Example of a Carmichael Number (561) - 12.5.1 | 12. Introduction to Fermat’s Little Theorem and Primality Testing | Discrete Mathematics - Vol 3
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Practice Questions

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Question 1

Easy

State Fermat's Little Theorem.

💡 Hint: Think about the relation between primes and modular arithmetic.

Question 2

Easy

What is an example of a Carmichael number?

💡 Hint: Recall that it misleads primality tests while being composite.

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Interactive Quizzes

Engage in quick quizzes to reinforce what you've learned and check your comprehension.

Question 1

What does Fermat's Little Theorem state?

  • If p is prime
  • then a^p ≡ 0 (mod p)
  • If p is prime
  • then a^(p-1) ≡ 1 (mod p)
  • If a is even
  • a^2 is even

💡 Hint: Remember the key formula in the theorem.

Question 2

Is 561 a prime number?

  • True
  • False

💡 Hint: Recollect the definition of prime numbers.

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Challenge Problems

Push your limits with challenges.

Question 1

Prove that if a number n satisfies b^(n-1) ≡ 1 for all bases b co-prime to n, then n is a Carmichael number.

💡 Hint: Use the prime factorization of n and analyze the implications for all bases.

Question 2

In a practical application, explain how one could modify a basic primality test to take Carmichael numbers into account.

💡 Hint: Consider the diversity of bases used in testing.

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