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JEE Advanced · Mathematics · 3. Complex Numbers

Paragraph:
Let \(A, B, C\) be three sets of complex numbers as defined below.
\(A=\{z ; \operatorname{lm} z \geq 1\} ; B=\{z:|z-2-i|=3\} ;\) \(C=\{z: \operatorname{Re}((1-i) z)=\sqrt{2}\}\).
Question:
The number of elements in the set \(A \cap B \cap C\) is

  1. A 0
  2. B 1
  3. C 2
  4. D \(\infty\)
Verified Solution

Answer & Solution

Correct Answer

(B) 1

Step-by-step Solution

Detailed explanation

Let \(z=x+i y\)
Set \(A\) corresponds to the region \(y \geq 1\).
Set \(B\) consists of points lying on the circle, centred at \((2,1)\) and radius 3 , i.e., \(x^2+y^2-4 x-2 y=4\)
Set \(C\) consists of points lying on the \(x+y=\sqrt{2}\)

Clearly, there is only one point of intersection of the line
\(x+y=\sqrt{2}\) and circle \(x^2+y^2-4 x-2 y=4 .\)
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