JEE AdvancedMathematicsComplex NumbersNumerical+4 / −1
If z is any complex number satisfying , then the minimum value of is
Numerical answer
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Correct answer: 5
- Let us rewrite the given condition in a more useful form.
Given which means
So, in the Argand plane, lies inside or on the circle with:
- center
- radius
- Now simplify the expression whose minimum is required:
But it is cleaner to factor directly:
Hence
So we need the minimum of the distance from to the fixed point multiplied by .
- Find the distance between the center of the allowed circle and the point .
- The minimum distance from a fixed point outside a circle to any point on or inside the circle is:
provided .
Here, so
- Therefore,
- Final answer:
Comparison with stored correct answer:
- Derived answer =
- Stored correct answer =
- They agree.
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