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If z is any complex number satisfying `| z - 3- 2i | le 1 ` then the minimum value of `| 2 z - 6 + 5i|` is

A

5

B

6

C

7

D

0

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The correct Answer is:
To solve the problem, we need to find the minimum value of \( |2z - 6 + 5i| \) given that \( |z - (3 + 2i)| \leq 1 \). ### Step-by-Step Solution: 1. **Understanding the Given Condition**: The condition \( |z - (3 + 2i)| \leq 1 \) describes a circle in the complex plane centered at the point \( (3, 2) \) with a radius of 1. This means that the complex number \( z \) can take any value within or on the boundary of this circle. 2. **Rewriting the Expression**: We need to minimize \( |2z - 6 + 5i| \). We can rewrite this expression: \[ |2z - 6 + 5i| = |2(z - 3 + \frac{5}{2}i)| \] This simplifies to: \[ 2|z - (3 - \frac{5}{2}i)| \] 3. **Finding the Center of the New Circle**: The center of the circle for \( z \) is \( (3, 2) \) and we need to find the distance from this center to the point \( (3, -\frac{5}{2}) \). 4. **Calculating the Distance**: The distance between the points \( (3, 2) \) and \( (3, -\frac{5}{2}) \) is calculated as follows: \[ \text{Distance} = |2 - (-\frac{5}{2})| = |2 + \frac{5}{2}| = |2 + 2.5| = |4.5| = \frac{9}{2} \] 5. **Considering the Radius**: Since the radius of the circle described by \( |z - (3 + 2i)| \leq 1 \) is 1, the minimum distance from the center \( (3, 2) \) to the point \( (3, -\frac{5}{2}) \) is: \[ \text{Minimum distance} = \frac{9}{2} - 1 = \frac{7}{2} \] 6. **Final Calculation**: Since we have \( 2|z - (3 - \frac{5}{2}i)| \), we multiply the minimum distance by 2: \[ \text{Minimum value of } |2z - 6 + 5i| = 2 \times \frac{7}{2} = 7 \] ### Conclusion: The minimum value of \( |2z - 6 + 5i| \) is \( 7 \).
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