Verified Solution • 2025–26 Session moderate

QJEEM23Ma686c: JEE Main 2023 Mathematics - Class 11 JEEM23Ma686c Solution: For a ∈ C , let A = { z ∈ C : Re ( a + z ¯ ) > Im ( a ¯ + z ) } …

For a∈C, let A={z∈C:Re(a+z¯)>Im(a¯+z)} and B={z∈C:Re(a+z¯)<Im(a¯+z)}. Then among the two statements :

(S1): If Re(a),Im(a)>0, then the set A contains all the real numbers

(S2) : If Re(a),Im(a)<0, then the set B contains all the real numbers,

Multiple Choice Options

  • A both are false
  • B only (S1) is true
  • C only (S2) is true
  • D both are true

Step-by-Step Verified Solution

We are given that a∈Ca \in \mathbb{C} and z∈Cz \in \mathbb{C} .

Let a=x1+iy1a = x_1 + iy_1 and z=x2+iy2z = x_2 + iy_2 where x1,y1,x2,y2∈Rx_1, y_1, x_2, y_2 \in \mathbb{R}

We are also given two sets A and B defined as follows :

- A is the set of all complex numbers zz for which the real part of (a+z‾)(a + \overline{z}) is greater than the imaginary part of (a‾+z)(\overline{a} + z) .

- B is the set of all complex numbers zz for which the real part of (a+z‾)(a + \overline{z}) is less than the imaginary part of (a‾+z)(\overline{a} + z) .

Statement (S1) says : If the real part and imaginary part of aa are both positive, then the set A contains all the real numbers.

Statement (S2) says : If the real part and imaginary part of aa are both negative, then the set B contains all the real numbers.

We need to determine which of these statements are true.

Let's evaluate each statement.

1. Statement (S1) : For z∈Az \in A ,

Re(a + \overline{z}) &gt; Im(\overline{a} + z)

This can be re-written as x_1 + x_2 &gt; y_2 - y_1

If we consider only real z (i.e. y2=0y_2 = 0 ) and given that x_1, y_1 &gt; 0 , then the condition simplifies to x_2 &gt; -(x_1 + y_1) .

This indicates that A covers a part of the negative real axis, but not the entire real axis. Therefore, Statement (S1) is false.

2. Statement (S2) : For z∈Bz \in B ,

Re(a + \overline{z}) &lt; Im(\overline{a} + z)

This can be re-written as x_1 + x_2 &lt; y_2 - y_1

If we consider only real z (i.e. y2=0y_2 = 0 ) and given that x_1, y_1 &lt; 0 , then the condition simplifies to x_2 &lt; -(x_1 + y_1) .

This indicates that B covers a part of the positive real axis, but not the entire real axis. Therefore, Statement (S2) is false.

Therefore, both (S1) and (S2) are false, so the answer is Option A : both are false.

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