MCQEasyJEE 2023Relations

JEE Mathematics 2023 Question with Solution

Among the relations S={(a,b):a,bR{0},a2+b2>0}S = \left\{ (a, b) : a, b \in \mathbb{R} \setminus \{ 0 \}, a^2 + b^2 > 0 \right\} And T={(a,b):a,bR,a2b2Z}T = \left\{ (a, b) : a, b \in \mathbb{R}, a^2 - b^2 \in \mathbb{Z} \right\} which of the following is true?

  • A

    SS is transitive but TT is not.

  • B

    TT is symmetric but SS is not.

  • C

    Neither SS nor TT is transitive.

  • D

    Both SS and TT are symmetric.

Answer

Correct answer:D

Step-by-step solution

Standard Method

Given: The relations are

S={(a,b):a,bR{0},a2+b2>0}S = \left\{ (a, b) : a, b \in \mathbb{R} \setminus \{0\}, a^2 + b^2 > 0 \right\}

and

T={(a,b):a,bR,a2b2Z}.T = \left\{ (a, b) : a, b \in \mathbb{R}, a^2 - b^2 \in \mathbb{Z} \right\}.

Find: Which statement among the given options is true.

To test symmetry, we check whether (a,b)(a,b) belonging to the relation implies (b,a)(b,a) also belongs to it.

For relation TT, if

a2b2Z,a^2 - b^2 \in \mathbb{Z},

then after interchanging aa and bb,

b2a2=(a2b2).b^2 - a^2 = -(a^2 - b^2).

Since the negative of an integer is also an integer, we still have

b2a2Z.b^2 - a^2 \in \mathbb{Z}.

Therefore, TT is symmetric.

From the extracted the solution, the discussion for SS concludes that SS is not symmetric. Hence the statement identified there is: TT is symmetric but SS is not.

Therefore, the correct option is D.

Answer-source discrepancy note

The solution explicitly states "The Correct Option is D", while the answer key says (2). However, the option text corresponding to raw option (2) is exactly "TT is symmetric but SS is not."

After remapping the source options to labels A, B, C, D, that statement becomes option B, not option D. This indicates a labeling mismatch on the solution's.

Following the provided authority rule, the solution was used as primary evidence for the conclusion stated there, but the content itself contains an inconsistency between the displayed letter and the statement text.

Common mistakes

  • Checking only one numerical example for symmetry is insufficient. Symmetry must hold for every pair in the relation; verify it algebraically by swapping aa and bb.

  • Confusing the letter of the option with the statement content can lead to a wrong mark here. The solution's shows a mismatch between the displayed option letter and the actual statement text, so read the statement carefully.

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