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For two non-zero complex numbers z(1) an...

For two non-zero complex numbers `z_(1)` and `z_(2)`,if `Re(z_(1)z_(2))=0` and `Re(z_(1)+z_(2))=0`,then which of the following are possible?
A. `Im(z_(1))>0` and `Im(z_(2))>0`
B. `lm(z_(1))>0` and `Im(z_(2))>0`
C. `lm(z_(1))>0` and `lm(z_(2))<0`
D. `Im(z_(1))<0` and `lm(z_(2))<0`
Choose the correct answer from the options given below :

A

`A` and `B`

B

`B` and `C`

C

` B` and `D`

D

`A` and `C`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we start with two non-zero complex numbers \( z_1 \) and \( z_2 \). We know that: 1. \( \text{Re}(z_1 z_2) = 0 \) 2. \( \text{Re}(z_1 + z_2) = 0 \) Let's express \( z_1 \) and \( z_2 \) in terms of their real and imaginary parts: \[ z_1 = x_1 + i y_1 \] \[ z_2 = x_2 + i y_2 \] where \( x_1, x_2 \) are the real parts and \( y_1, y_2 \) are the imaginary parts of \( z_1 \) and \( z_2 \), respectively. ### Step 1: Analyze \( \text{Re}(z_1 z_2) = 0 \) Calculating \( z_1 z_2 \): \[ z_1 z_2 = (x_1 + i y_1)(x_2 + i y_2) = x_1 x_2 + i (x_1 y_2 + y_1 x_2) - y_1 y_2 \] The real part of \( z_1 z_2 \) is: \[ \text{Re}(z_1 z_2) = x_1 x_2 - y_1 y_2 \] Given that \( \text{Re}(z_1 z_2) = 0 \), we have: \[ x_1 x_2 - y_1 y_2 = 0 \quad \text{(1)} \] ### Step 2: Analyze \( \text{Re}(z_1 + z_2) = 0 \) Calculating \( z_1 + z_2 \): \[ z_1 + z_2 = (x_1 + x_2) + i (y_1 + y_2) \] The real part of \( z_1 + z_2 \) is: \[ \text{Re}(z_1 + z_2) = x_1 + x_2 \] Given that \( \text{Re}(z_1 + z_2) = 0 \), we have: \[ x_1 + x_2 = 0 \quad \text{(2)} \] From equation (2), we can express \( x_2 \) in terms of \( x_1 \): \[ x_2 = -x_1 \] ### Step 3: Substitute \( x_2 \) into equation (1) Substituting \( x_2 = -x_1 \) into equation (1): \[ x_1 (-x_1) - y_1 y_2 = 0 \] This simplifies to: \[ -x_1^2 - y_1 y_2 = 0 \] Rearranging gives: \[ y_1 y_2 = -x_1^2 \quad \text{(3)} \] ### Step 4: Analyze the implications of equation (3) Since \( x_1^2 \) is always non-negative, \( y_1 y_2 \) must be negative. This means that \( y_1 \) and \( y_2 \) have opposite signs. ### Conclusion From the analysis, we conclude: - If \( y_1 > 0 \) (i.e., \( \text{Im}(z_1) > 0 \)), then \( y_2 < 0 \) (i.e., \( \text{Im}(z_2) < 0 \)). - Conversely, if \( y_1 < 0 \), then \( y_2 > 0 \). Thus, the only possible combinations of the imaginary parts of \( z_1 \) and \( z_2 \) are: - \( \text{Im}(z_1) > 0 \) and \( \text{Im}(z_2) < 0 \) - \( \text{Im}(z_1) < 0 \) and \( \text{Im}(z_2) > 0 \) ### Possible Options Now, let's evaluate the options given: A. \( \text{Im}(z_1) > 0 \) and \( \text{Im}(z_2) > 0 \) - **Not possible** B. \( \text{Im}(z_1) > 0 \) and \( \text{Im}(z_2) > 0 \) - **Not possible** C. \( \text{Im}(z_1) > 0 \) and \( \text{Im}(z_2) < 0 \) - **Possible** D. \( \text{Im}(z_1) < 0 \) and \( \text{Im}(z_2) < 0 \) - **Not possible** Thus, the correct answer is **C**.
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