DIVISIBILITY CONGRUENCE question

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In summary, divisibility congruence is a mathematical concept that states if two numbers are divisible by the same number, then they leave the same remainder when divided by that number. It is a special case of regular congruence, where the modulus must also be a factor of the numbers being compared. Divisibility congruence is used in number theory to prove theorems and solve problems related to divisibility, prime numbers, and modular arithmetic. It can also be applied to fractions, known as rational congruence.
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Question: If gcd(a,42)=1, show that a^6 - 1 is divisible by 168.

Answer: So I know that if 42 were prime, than the Little Fermat Thm says that a^p-1 is congruent to 1 mod p. But I have no idea where to start if p is not prime. Help please.
 
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prove the divisibility by 3, 7 and 8 separately. 3 and 7 can be done with Little Fermat's theorem.
For divisibility by 8, factor a^6 -1.
 

1. What is the definition of divisibility congruence?

Divisibility congruence is a mathematical concept that states that if two numbers are divisible by the same number, then they leave the same remainder when divided by that number. In other words, if a and b are both divisible by n, then a and b are congruent modulo n.

2. How is divisibility congruence different from regular congruence?

Divisibility congruence is a special case of regular congruence, where the modulus (n) is also a factor of the numbers being compared. In regular congruence, the modulus can be any positive integer, but in divisibility congruence, it must be a factor of the numbers being compared.

3. What are some examples of divisibility congruence?

One example is that 15 is congruent to 5 modulo 10, since both 15 and 5 leave a remainder of 5 when divided by 10. Another example is that 24 is congruent to 12 modulo 6, since both 24 and 12 are divisible by 6.

4. How is divisibility congruence used in number theory?

Divisibility congruence is a fundamental concept in number theory, which is the branch of mathematics that deals with the properties and relationships of numbers. It is used to prove theorems and solve problems related to divisibility, prime numbers, and modular arithmetic.

5. Can divisibility congruence be applied to fractions?

Yes, divisibility congruence can also be applied to fractions. For example, if two fractions have the same denominator and their numerators are congruent modulo the denominator, then the fractions are also congruent. This concept is known as rational congruence.

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