Q. 324.7( 3 Votes )
Let us define a relation R in R as aRb if a ≥ b. Then R is
A. an equivalence relation
B. reflexive, transitive but not symmetric
C. symmetric, transitive but
D. neither transitive nor reflexive not reflexive but symmetric.
Answer :
Given that, aRb if a ≥ b
Now,
We observe that, a ≥ a since every a ∈ R is greater than or equal to itself.
⇒ a ≥ a ⇒ (a,a) ∈ R ∀ a ∈ R
⇒ R is reflexive.
Let (a,b) ∈ R
⇒ a ≥ b
But b cannot be greater than a if a is greater than b.
⇒ (b,a) ∉ R
For e.g., we observe that (5,2) ∈ R i.e 5 ≥ 2 but 2 ≱ 5 ⇒ (2,5) ∉ R
⇒ R is not symmetric
Let (a,b) ∈ R and (b,c) ∈ R
⇒ a ≥ b and b ≥ c
⇒ a ≥ c
⇒ (a,c) ∈ R
For e.g., we observe that
(5,4) ∈ R ⇒ 5 ≥ 4 and (4,3) ∈ R ⇒ 4 ≥ 3
And we know that 5 ≥ 3 ∴ (5,3) ∈ R
⇒ R is transitive.
Thus, R is reflexive, transitive but not symmetric.
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