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CGP EDU Academic Team
Published on: August 14, 2026
If ƒ(x) is a function satisfying ƒ(x + y) = ƒ(x) ƒ(y) for all x, y ∈ N such that ƒ(1) = 3 and 
= 120. Then the value of n is –
Text Solution
Verified by ExpertsThe correct answer is:
A
Given, ƒ(x + y) = ƒ(x) ƒ(y) for all x, y ∈ N
∴ for any x ∈ N, ƒ(x) = [ƒ(1)] x = 3 x [ ƒ(1) = 3]
Since 
= 120
⇒ 
= 120
⇒ 3 1 + 3 2 + 3 3 + …..+ 3 n = 120
⇒ 3 n – 1 = 80
⇒ 3n = 81 = 3 4 ⇒ n = 4.
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