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JEE Advanced
Exam
JEE Advanced
Subject
Mathematics
Chapter
Sets and Relations

JEE Advanced · Mathematics · Sets and Relations

Let P (S) denote the power set of S = \ 1, 2, 3, , 10\ . Define the...

Let PP\left(S\right)denotethepowersetofdenote the power set ofS = \left\{1, 2, 3, \ldots , 10\right\}.Definetherelations. Define the relations{R}_{1} and~and{R}_{2} on~onP\left(S\right)asasA{R}_{1}Bifif\left(A \cap B^{c}\right) \cup \left(B \cap A^{c}\right) = ϕ and AR2BA{R}_{2}B if A∪Bc=B∪Ac,∀A,B∈P(S)A \cup B^{c} = B \cup A^{c}, \forall A, B \in P\left(S\right) . Then :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 R _ 1 B ifLet 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 R _ 1 B if

Options

  1. Aboth R1{R}_{1}~and R2{R}_{2}& are equivalence relations
  2. Bonly R1{R}_{1}& is an equivalence relation
  3. Conly R2{R}_{2}& is an equivalence relation
  4. Dboth R1{R}_{1}~and R2{R}_{2}& are not equivalence relations

Correct answer

A. both R1{R}_{1}~and R2{R}_{2}& are equivalence relations

Step-by-step solution

Given,

S={1,2,3,……10}S = \left\{1, 2, 3, \ldots \ldots 10\right\}

P(S)=P\left(S\right) = power set of SS

AR1B⇒(A∩Bc)∪(Ac∩B)=ϕA{R}_{1}B ⇒ \left(A \cap B^{c}\right) \cup \left(A^{c} \cap B\right) = ϕ

Now for reflexive property, replacing~BB~with~AA~we get,

\left(A \cap A^{c}\right) \cup \left(A^{c} \cap A\right) which ~which~ϕ always,</p><p>Nowcheckingsymmetricwewillinterchange ~always,</p><p>Now checking symmetric we will interchange~A \text{ and } B,</p><p>So,~ \left(B \cap A^{c}\right) \cup \left(B^{c} \cap A\right)~which is same as~ \left(A \cap B^{c}\right) \cup \left(A^{c} \cap B\right), hence the relation is symmetric,

So,~R1{R}_{1}~is reflexive, symmetric

Now checking for transitive
\left(A \cap B^{c}\right) \cup \left(A^{c} \cap B\right) = ϕ;</p><p>Now from diagram the elements in~ \left(A \cap B^{c}\right) \cup \left(A^{c} \cap B\right) willbe,</p><p>{a}∪{b}~will be,</p><p>\left\{a\right\} \cup \left\{b\right\}~which is given as empty set~ϕϕ

Hence, we can say that,~\left\{a\right\} = ϕ = \left\{b\right\} ⇒ A = B</p><p>Nowtaking, </p><p>Now taking,~( B \cap C^{c} ) \cup ( B^{c} \cap C ) = ϕ ∴ B = C</p><p></p><p>∴ A = Cequivalence.</p><p><imgsrc="/api/proxy−image?url=httpsequivalence.</p><p><img src="/api/proxy-image?url=https%3A%2F%2Ffirebasestorage.googleapis.com%2Fv0%2Fb%2Fquantrexacademy-app.firebasestorage.app%2Fo%2Fquestions%252Ffigs%252Fpyq%252Fjee_main%252F7dda9698-159e-473c-a185-7b6eb321b64c-9896795.png%3Falt%3Dmedia \text{ and } clean=1 \text{ and } v=qxfig138" style="width: 250px; height: 219px;" / data-qx-orig-src="/assets/diagrams/qx-book-88e1f37a7b7f8ede.png" data-qx-storage-src="/assets/diagrams/qx-book-88e1f37a7b7f8ede.png"></p><p>~</p><p>Now solving,</p><p>{R}_{2} ≡ A \cup B^{c} = A^{c} \cup B</p><p>Nowforreflexivereplacing </p><p>Now for reflexive replacing~B \to A weget,</p><p>~we get,</p><p>A \cup A^{c} = A^{c} \cup A whichistrue,</p><p>Andforsymmetricinterchanging ~which is true,</p><p>And for symmetric interchanging~A ⇔ B weget,</p><p>~we get,</p><p>B \cup A^{c} = B^{c} \cup A whichisagaintrue,</p><p>Hence, ~which is again true,</p><p>Hence,~{R}_{2} \toReflexive,symmetric</p><p><imgsrc="/api/proxy−image?url=httpsReflexive, symmetric</p><p><img src="/api/proxy-image?url=https%3A%2F%2Ffirebasestorage.googleapis.com%2Fv0%2Fb%2Fquantrexacademy-app.firebasestorage.app%2Fo%2Fquestions%252Ffigs%252Fpyq%252Fjee_main%252Ff85793dd-c45c-48ad-94cd-a80954a303c0-9896795_2.png%3Falt%3Dmedia \text{ and } clean=1 \text{ and } v=qxfig138" style="width: 250px; height: 219px;" / data-qx-orig-src="/assets/diagrams/qx-book-90df37c29fd02696.png" data-qx-storage-src="/assets/diagrams/qx-book-90df37c29fd02696.png"></p><p>Now for transitive,</p><p>From diagram the elements inA \cup B^{c} = A^{c} \cup B ⇒ \left\{a, c, d\right\} = \left\{b, c, d\right\}</p><p>Oncomparingbothside,weget {a}={b}∴A=B</p><p>On comparing both side, we get~\left\{a\right\} = \left\{b\right\} ∴ A = B

And,~B∪Cc=Bc∪C⇒B=CB \cup C^{c} = B^{c} \cup C ⇒ B = C

∴A=C∴A∪Cc=Ac∪C∴ A = C ∴ A \cup C^{c} = A^{c} \cup C

∴∴ Equivalence

Hence, both given relation are equivalence.

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