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JEE Main 202313 AprilEvening Shift
Exam
JEE Main
Year
2023
Date
13 April
Shift
Evening Shift
Subject
Mathematics
Chapter
Sets and Relations

JEE Main 2023 · 13 April · Evening Shift · Mathematics · Sets and Relations

Let A = - 4, - 3, - 2, 0, 1, 3, 4 and R = \ ( a, b ) ∈ A × A : b =...

Let A = { - 4, - 3, - 2, 0, 1, 3, 4 } and R={(a,b)∈A×A:b=∣a∣ or b2=a+1}R = \{ ( a, b ) \in A \times A : b = | a |\text{ or } {b}^{2} = a + 1\} be a relation on AA. Then the minimum number of elements, that must be added to the relation RR so that it becomes reflexive and symmetric, is

Correct answer

7

Step-by-step solution

Given,

A = { - 4, - 3, - 2, 0, 1, 3, 4 } and R={(a,b)∈A×A:b=∣a∣ or b2=a+1}R = \{ ( a, b ) \in A \times A : b = | a |\text{ or } {b}^{2} = a + 1\} be a relation on AA,

So, the relation is given by,

R=(−4,4),(−3,3),(0,0),(1,1),(3,3),(4,4),(0,1),(3,−2)R = { ( - 4, 4 ) , ( - 3, 3 ) , ( 0, 0 ) , ( 1, 1 ) , ( 3, 3 ) , ( 4, 4 ) , ( 0, 1 ) , ( 3, - 2 ) }

Now, relation to be reflexive (a,a)∈R∀a∈A( a, a ) \in R \forall a \in A

⇒(−4,−4),(−3,−3),(−2,−2)⇒ ( - 4, - 4 ) , ( - 3, - 3 ) , ( - 2, - 2 ) also should be added in RR.

Now relation to be symmetric if (a,b)∈R( a, b ) \in R, then (b,a)∈R∀a,b∈A( b, a ) \in R \forall a, b \in A

⇒(4,−4),(3,−3),(1,0),(−2,3)⇒ ( 4, - 4 ) , ( 3, - 3 ) , ( 1, 0 ) , ( - 2, 3 ) also should be added in RR

Hence, minimum number of elements to be added to
R = 3 + 4 = 7

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