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Let f be a non-constant entire function such that |f(z)| = 1 for |z| = 1.Let U denote the open unit disk around 0.Which of the following is FALSE ?
Question

Let f be a non-constant entire function such that |f(z)| = 1 for |z| = 1.

Let U denote the open unit disk around 0.

Which of the following is FALSE ?

A.

f(z) = C .

B.

f has at least one zero in U .

C.

f has at most finitely many distinct zeros in C .

D.

f can have a zero outside U.

Correct option is D

f(z) is a non-constant entire functionsuch that

|f(z)| = 1 for |z| = 1.U = {z ∈ C | |z| < 1}

According to the given condition f(z) will look like:f(z) = znz^n​ ; ∀z ∈ C .

Stepwise Analysis:

• Option (A) : As f(c) = c True.

• Option (B) : f(z) = 0 ==> z = 0 , so f has at least one zero in U True.

• Options (C) and (D) : clearly f can have at most finitely many distinctzeros in C,

but f(z) cannot have a zero outside USo, Statement (D) is false

==> Option (D) is correct.

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