Let P S denote the power set of S = 1 , 2 , 3 , … , 10 . Define the relations R 1 and R 2 on P S as A…

Let PS denote the power set of S=1,2,3,,10. Define the relations R1 and R2 on PS as AR1B if ABcBAc=ϕ and AR2 B if ABc=BAc,A,BPS . Then :
  1. both R1 and R2 are equivalence relations
  2. only R1 is an equivalence relation
  3. only R2 is an equivalence relation
  4. both R1 and R2 are not equivalence relations

Solution

Given,

S=1,2,3,10

PS= power set of S

AR1BABcAcB=ϕ

Now for reflexive property, replacing B with A we get,

AAcAcA which ϕ always,

Now checking symmetric we will interchange A & B,

So, BAcBcA which is same as ABcAcB, hence the relation is symmetric,

So, R1 is reflexive, symmetric

Now checking for transitive
ABcAcB=ϕ;

Now from diagram the elements in ABcAcB will be,

ab which is given as empty set ϕ

Hence, we can say that, a=ϕ=bA=B

Now taking, (BCc)(BcC)=ϕB=C

  A=C equivalence.

 

Now solving,

R2ABc=AcB

Now for reflexive replacing BA we get,

AAc=AcA which is true,

And for symmetric interchanging AB we get,

BAc=BcA which is again true,

Hence, R2 Reflexive, symmetric

Now for transitive,

From diagram the elements inABc=AcBa,c,d=b,c,d

On comparing both side, we get a=b   A=B

And, BCc=BcCB=C

  A=C    ACc=AcC

  Equivalence

Hence, both given relation are equivalence.

Asked in: JEE Main 2023 (01 Feb Shift 2)

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