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GATE 2026 MA – Question 17

Complex Analysis · Analytic and Harmonic Functions · 1 mark · Multiple choice

$f:\mathbb C\to\mathbb C$ is $f(z)=|z|^2-5\bar z+2$. At which listed point is f complex differentiable?

  1. 5i
  2. 5
  3. −5i
  4. −5

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Correct answer: (B) 5

Explanation

Write z = x+iy. Then u = x²+y²−5x+2 and v = 5y. Cauchy–Riemann requires 2x−5 = 5 and 2y = 0. Thus x = 5,y = 0. The partials are continuous, so differentiability holds at **z = 5, B**.

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