InterviewSolution
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Mark the tick against the correct answer in the following: Let S be the set of all real numbers and let R be a relation on S defined by a R b ⇔ |a| ≤ b. Then, R is A. reflexive but neither symmetric nor transitive B. symmetric but neither reflexive nor transitive C. transitive but neither reflexive nor symmetric D. none of these |
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Answer» Correct Answer is (C) transitive but neither reflexive nor symmetric Given set S = {…….,-2,-1,0,1,2 …..} And R = {(a, b) : a,b ∈ S and |a| ≤ b } Formula For a relation R in set A Reflexive The relation is reflexive if (a , a) ∈ R for every a ∈ A Symmetric The relation is Symmetric if (a , b) ∈ R , then (b , a) ∈ R Transitive Relation is Transitive if (a , b) ∈ R & (b , c) ∈ R , then (a , c) ∈ R Equivalence If the relation is reflexive , symmetric and transitive , it is an equivalence relation. Check for reflexive Consider , (a,a) ∴ |a| ≤ a and which is not always true. Ex_if a=-2 ∴ |-2| ≤ -2 ⇒ 2 ≤ -2 which is false Therefore , R is not reflexive ……. (1) Check for symmetric a R b ⇒ |a| ≤ b b R a ⇒ |b| ≤ a Both cannot be true. Ex _ If a=-2 and b=-1 ∴ 2 ≤ -1 is false and 1 ≤ -2 which is also false Therefore , R is not symmetric ……. (2) Check for transitive a R b ⇒ |a| ≤ b a R b ⇒ |a| ≤ b ∴ |a| ≤ c Ex _a=-5 , b= 7 and c=9 ∴ 5 ≤ 7 , 7 ≤ 9 and hence 5 ≤ 9 Therefore , R is transitive ……. (3) Now , according to the equations (1) , (2) , (3) Correct option will be (C) |
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