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Let z1, z2 be two complex numbers repres...

Let `z_1, z_2` be two complex numbers represented by points on the circle `|z_1|= and and |z_2|=2` are then

A

`max.|2z_(1)+z_(2)|=4`

B

`min.|z_(1)+z_(2)|=1`

C

`|z_(2)+(1)/(z_(1))|le3`

D

`|z_(1)+(2)/(z_(2))|le2`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem step by step, we need to analyze the given complex numbers \( z_1 \) and \( z_2 \) which lie on circles defined by their moduli. ### Step 1: Understanding the Moduli Given: - \( |z_1| = 1 \) (This means \( z_1 \) lies on the unit circle) - \( |z_2| = 2 \) (This means \( z_2 \) lies on a circle of radius 2) ### Step 2: Analyzing Maximum of \( |2z_1 + z_2| \) To find the maximum value of \( |2z_1 + z_2| \): - We can use the triangle inequality: \[ |2z_1 + z_2| \leq |2z_1| + |z_2| = 2|z_1| + |z_2| = 2 \cdot 1 + 2 = 4 \] - Thus, the maximum value of \( |2z_1 + z_2| \) is \( 4 \). ### Step 3: Analyzing Minimum of \( |z_2 - z_1| \) To find the minimum value of \( |z_2 - z_1| \): - The minimum distance occurs when \( z_2 \) and \( z_1 \) are aligned in the same direction: \[ |z_2 - z_1| \geq ||z_2| - |z_1|| = |2 - 1| = 1 \] ### Step 4: Analyzing \( |z_2 + \frac{1}{z_1}| \) To find \( |z_2 + \frac{1}{z_1}| \): - Since \( |z_1| = 1 \), we have \( |\frac{1}{z_1}| = 1 \). - Therefore: \[ |z_2 + \frac{1}{z_1}| \leq |z_2| + |\frac{1}{z_1}| = 2 + 1 = 3 \] ### Step 5: Analyzing \( |z_1 + 2z_2| \) To find \( |z_1 + 2z_2| \): - Using the triangle inequality: \[ |z_1 + 2z_2| \leq |z_1| + |2z_2| = 1 + 2 \cdot 2 = 5 \] - However, we need to check if it is less than or equal to 2, which is not true. ### Conclusion From the analysis: 1. Maximum \( |2z_1 + z_2| = 4 \) (True) 2. Minimum \( |z_2 - z_1| = 1 \) (True) 3. \( |z_2 + \frac{1}{z_1}| \leq 3 \) (True) 4. \( |z_1 + 2z_2| \leq 2 \) (False) ### Final Answers - The correct options are 1, 2, and 3.
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