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The relation R on the set of real numbers defined by R={(a,b):ab2}R = \{(a, b): a \leq b^2\} is

(A) Reflexive

(B) Not symmetric

(C) Neither reflexive nor transitive

(D) Transitive

Choose the correct answer from the options given below:

Solution

Correct Option: 3

The relation R on the set of real numbers is defined by R={(a,b):ab2}R = \{(a, b): a \leq b^2\}.

This means two numbers aa and bb are related if aa is less than or equal to bb squared.


For a relation to be reflexive, (a,a)(a, a) must be in RR for all real numbers aa.

For (a,a)(a, a) to be in RR: aa2a \leq a^2

Testing with a=0.5a = 0.5:

a=0.5a = 0.5

a2=(0.5)2=0.25a^2 = (0.5)^2 = 0.25

Is 0.50.250.5 \leq 0.25? No.

So (0.5,0.5)(0.5, 0.5) is not in RR.

RR is not reflexive. Statement (A) is false.


For a relation to be symmetric, if (a,b)(a, b) is in RR, then (b,a)(b, a) must also be in RR.

Testing with a=1,b=2a = 1, b = 2:

Check (1,2)(1, 2): Is 1221 \leq 2^2? Is 141 \leq 4? Yes.

So (1,2)(1, 2) is in RR.

Check (2,1)(2, 1): Is 2122 \leq 1^2? Is 212 \leq 1? No.

So (2,1)(2, 1) is not in RR.

RR is not symmetric. Statement (B) is true.


For a relation to be transitive, if (a,b)(a, b) is in RR and (b,c)(b, c) is in RR, then (a,c)(a, c) must also be in RR.

Testing with a=3,b=2,c=1.5a = 3, b = 2, c = 1.5:

Check (3,2)(3, 2): Is 3223 \leq 2^2? Is 343 \leq 4? Yes.

Check (2,1.5)(2, 1.5): Is 21.522 \leq 1.5^2? Is 22.252 \leq 2.25? Yes.

Check (3,1.5)(3, 1.5): Is 31.523 \leq 1.5^2? Is 32.253 \leq 2.25? No.

Even though (3,2)(3, 2) and (2,1.5)(2, 1.5) are both in RR, (3,1.5)(3, 1.5) is not in RR.

RR is not transitive. Statement (D) is false.


Since RR is not reflexive and not transitive, statement (C) "Neither reflexive nor transitive" is true.

The true statements are (B) and (C).

Therefore, the correct answer is Option 3.

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