Prove ## a/d\equiv b/d \mod n/d ##.

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In summary, congruence relations are represented by the notation "a/d≡b/d (mod n/d)" and can be proven using the definition of congruence. Proving these relations is important in simplifying equations and identifying patterns. A real-life example of proving a congruence relation is showing that 17/3≡5/3 (mod 4/3). Congruence relations have various applications in fields such as cryptography, computer science, and physics.
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Math100
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Homework Statement
Prove the following assertion:
If ## a\equiv b \mod n ## and the integers ## a, b, n ## are all divisible by ## d>0 ##, then ## a/d\equiv b/d \mod n/d ##.
Relevant Equations
None.
Proof:

Suppose ## a\equiv b \mod n ## and the integers ## a, b, n ## are all divisible by ## d>0 ##.
Then ## n\mid (a-b)\implies mn=a-b ## for some ## m\in\mathbb{Z} ##.
Note that ## a=id\implies \frac{a}{d}=i ##, ## b=jd\implies \frac{b}{d}=j ##, and ## n=kd\implies \frac{n}{d}=k ## for some ## i, j, k\in\mathbb{Z} ##.
Thus ## id-jd=m(kd)\implies i-j=mk\implies \frac{a}{d}-\frac{b}{d}=m\frac{n}{d}\implies \frac{a}{d}\equiv \frac{b}{d} \mod \frac{n}{d} ##.
Therefore, if ## a\equiv b \mod n ## and the integers ## a, b, n ## are all divisible by ## d>0 ##, then ## a/d\equiv b/d \mod n/d ##.
 
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Math100 said:
Homework Statement:: Prove the following assertion:
If ## a\equiv b \mod n ## and the integers ## a, b, n ## are all divisible by ## d>0 ##, then ## a/d\equiv b/d \mod n/d ##.
Relevant Equations:: None.

Proof:

Suppose ## a\equiv b \mod n ## and the integers ## a, b, n ## are all divisible by ## d>0 ##.
Then ## n\mid (a-b)\implies mn=a-b ## for some ## m\in\mathbb{Z} ##.
Note that ## a=id\implies \frac{a}{d}=i ##, ## b=jd\implies \frac{b}{d}=j ##, and ## n=kd\implies \frac{n}{d}=k ## for some ## i, j, k\in\mathbb{Z} ##.
Thus ## id-jd=m(kd)\implies i-j=mk\implies \frac{a}{d}-\frac{b}{d}=m\frac{n}{d}\implies \frac{a}{d}\equiv \frac{b}{d} \mod \frac{n}{d} ##.
Therefore, if ## a\equiv b \mod n ## and the integers ## a, b, n ## are all divisible by ## d>0 ##, then ## a/d\equiv b/d \mod n/d ##.
That's fine.

Edit: Only remark: the product "id" is a bit unlucky because ##id## often abbreviates the identity function.
 
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  • #3
fresh_42 said:
That's fine.

Edit: Only remark: the product "id" is a bit unlucky because ##id## often abbreviates the identity function.
I agree. I haven't thought about that before.
 

FAQ: Prove ## a/d\equiv b/d \mod n/d ##.

1. What does "a/d" mean in the expression "a/d\equiv b/d \mod n/d"?

In this expression, "a/d" represents the quotient of a divided by d. This means that the result of a/d is the integer value obtained when a is divided by d.

2. What does "b/d" mean in the expression "a/d\equiv b/d \mod n/d"?

Similar to "a/d", "b/d" represents the quotient of b divided by d. This means that the result of b/d is the integer value obtained when b is divided by d.

3. What does "n/d" mean in the expression "a/d\equiv b/d \mod n/d"?

In this expression, "n/d" represents the quotient of n divided by d. This means that the result of n/d is the integer value obtained when n is divided by d.

4. What does the symbol "\equiv" mean in the expression "a/d\equiv b/d \mod n/d"?

The symbol "\equiv" means "is congruent to" or "is equivalent to". In this context, it indicates that the two expressions on either side of it have the same remainder when divided by n/d.

5. What does "\mod n/d" mean in the expression "a/d\equiv b/d \mod n/d"?

The "\mod n/d" portion of the expression indicates that the congruence is being evaluated in modulo n/d. This means that the remainder of the division of a/d and b/d by n/d will be the same, and the two expressions are considered to be congruent in this modulo system.

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