Question

If A= { xIx ℇ N and a factor of 15 } and B = {1,10,30} then A ∩ B =​

Answer 1

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}

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

∴R is reflexive.

Now, let (a,b)∈R⇒∣a−b∣ is a multiple of 4.

⇒∣−(a−b)∣=∣b−a∣ is a multiple of 4.

⇒(b,a)∈R

∴ is symmetric.

Now, let (a,b),(b,c)∈R

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

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

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

⇒∣a−c∣ is a multiple of 4.

⇒(a,c)∈R.

∴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, and

∣9−1∣=8 is a multiple of 4

Hence, R is an equivalence relation.

Answer 2

Answer:

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