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Question: Answered & Verified by Expert
Let A={-4,-3,-2,0,1,3,4} and R={(a,b)A×A : b=|a| or b2=a+1 be a relation on A. Then the minimum number of elements, that must be added to the relation R so that it becomes reflexive and symmetric, is
MathematicsSets and RelationsJEE MainJEE Main 2023 (13 Apr Shift 2)
Solution:
2015 Upvotes Verified Answer
The correct answer is: 7

Given,

A={-4,-3,-2,0,1,3,4} and R={(a,b)A×A : b=|a| or b2=a+1 be a relation on A,

So, the relation is given by,

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  aA

(-4,-4),(-3,-3),(-2,-2) also should be added in R.

Now relation to be symmetric if (a,b)R, then (b,a)R  a,bA

(4,-4),(3,-3),(1,0),(-2,3) also should be added in R

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

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