The relation R on the set of real numbers defined by $R = \{(a, b): a ≤b^2\}$ is
(A) Reflexive
(B) Not symmetric
(C) Neither reflexive nor transitive
(D) Transitive
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (B) and (C) only
(B) Not symmetric
(C) Neither reflexive nor transitive
Given: Relation \( R = \{(a, b) : a \leq b^2\} \) on the set of real numbers \( \mathbb{R} \)
(A) Reflexive:
For reflexivity, we need: \( a \leq a^2 \) for all \( a \in \mathbb{R} \)
Counterexample: Take \( a = \frac{1}{2} \Rightarrow \frac{1}{2} \not\leq \left(\frac{1}{2}\right)^2 = \frac{1}{4} \)
So the relation is not reflexive.
(B) Symmetric:
We need: If \( a \leq b^2 \), then \( b \leq a^2 \)
Take \( a = 1, b = 2 \Rightarrow 1 \leq 4 \), but \( 2 \not\leq 1 \)
So the relation is not symmetric.
(C) Transitive:
We need: If \( a \leq b^2 \) and \( b \leq c^2 \), then \( a \leq c^2 \)
Take \( a = 5, b = 3, c = 2 \):
- \( 5 \leq 9 \) ✔️
- \( 3 \leq 4 \) ✔️
- \( 5 \leq 4 \) ❌
So the relation is not transitive.