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Show that the relation R in the set A = {x ∈ Z : 0 ≤ x ≤ 12} given by R = {(a, b) : |a − b| is a multiple of 4} is an equivalence relation. Find the set of all elements related to 1. - Mathematics

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प्रश्न

Show that the relation R in the set A = {x ∈ Z : 0 ≤ x ≤ 12} given by R = {(a, b) : |a − b| is a multiple of 4} is an equivalence relation. Find the set of all elements related to 1.

योग
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उत्तर

A = {x ∈ Z : 0 ≤ x ≤ 12} = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12}

R = {(a, b) : |a − b| is a multiple of 4}

(i) Reflexive:

For any element a ∈ A, we have (a, a) ∈ R as |a − a| = 0 is a multiple of 4.

∴ R is reflexive.

(ii) Symmetric:

Now, let (a, b) ∈ R

⇒ |a − b| is a multiple of 4.

⇒ |−(a − b)| = |b − a| is a multiple of 4.

⇒ (b, a) ∈ R

Thus (a, b) ∈ R 

⇒ (b, a) ∈ R

∴ R is symmetric.

(iii) Transitive:

Now, let (a, b), (b, c) ∈ R.

⇒ |a − b| is a multiple of 4 and |b − c| is a multiple of 4.

⇒ |a − c| = |a − b + b − c| = |a − b| + |b − c|

⇒ (a − c) = (a − b) + (b − c) is a multiple of 4.

⇒ (a, c) ∈ R  ...[∴ |a − b| is multiple of 4 and |b − c| is multiple of 4.]

∴ R is transitive.

Hence, R is an equivalence relation.

The set of elements related to 1 is {1, 5, 9} since

|1 − 1| = 0 is a multiple of 4.

|5 − 1| =  4 is a multiple of 4.

|9 − 1| =  8 is a multiple of 4.

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अध्याय 1: Relations and Functions - Exercise 1.1 [पृष्ठ ६]

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एनसीईआरटी Mathematics Part 1 and 2 [English] Class 12
अध्याय 1 Relations and Functions
Exercise 1.1 | Q 9.1 | पृष्ठ ६

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