IGNOU MMT 5 2026 - Determine whether each of the following statement is true or false. Ju

Question

Determine whether each of the following statement is true or false. Justify your answer with a short proof or a counter example.
i) If $z = a + ib$ , where a and b are integers, then $|1 + z + z^2 + \dots + z^n| \geq |z|^n$ if a > 0.
ii) If f(z) and $\overline{f(\bar{z})}$ are analytic functions in a domain, then f is necessarily a constant.
iii) A real-valued function u(x, y) is harmonic in D iff u(x, -y) is harmonic in D.
iv) $\lim_{n \to \infty} (n!)^{1/n} = \infty$ .
v) The inequality $|e^a - e^b| \leq |a - b|$ holds for $a, b \in D = \{w : \text{Re } w \leq 0\}$ .
vi) If $f(z) = \sum_{n=0}^{\infty} a_n(z - a)^n$ has the property that $\sum_{n=0}^{\infty} f^{(n)}(a)$ converges, then f is necessarily an entire function.
vii) If a power series $\sum_{n=0}^{\infty} a_n z^n$ converges for |z| < 1 and if $b_n \in \mathbb{C}$ is such that |b_n| < n² |a_n| for all $n \geq 0$ , then $\sum_{n=0}^{\infty} b_n z^n$ converges for |z| < 1.
viii) If f is entire and $f(z) = f(-z)$ for all z, then there exists an entire function g such that $f(z) = g(z^2)$ for all $z \in \mathbb{C}$ .
ix) A mobius transformation which maps the upper half plane $\{z : \text{Im } z > 0\}$ onto itself and fixing $0, \infty$ and no other points, must be of the form $Tz = \alpha z$ for some $\alpha > 0$ and $\alpha \neq 1$ .
x) If f is entire and $\text{Re } f(z)$ is bounded as $|z| \to \infty$ , then f is constant.

10 Jan 2026

Answer :

Word Count : 253

i) True. If (a > 0) and (a x + b = 0), then (x = -\frac{b}{a}) is a unique solution. ii) False. If (f(z)) and (g(z)) are analytic in a domain, (f(z) = g(z)) does not imply (f) is constant; for example, (f(z) = z) and (g(z) = z) are analytic but not constant. iii) True. If (u(x, y)) is harmonic ((\nabla^2 u = 0)), then (u(x, -y)) also satisfies (\frac{\partial^2 u}{\partial x^2} + \frac{\partial^2 u}{\partial (-y)^2} = 0), so it is harmonic. iv) Cannot determine. Statement is incomplete, so no conclusion can be made. v) True. For (|z| <

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