Misc 1 - Chapter 8 Class 11 Sequences and Series

Last updated at April 16, 2024 by

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Misc 1 If f is a function satisfying f (x + y) = f(x) f(y) for all x, y N such that f(1) = 3 and , find the value of n. Given that : f (x + y) = f(x) f(y) x, y N and f(1) = 3 f (1) = 3 f (2) = 9 = 3 2 f (3) = 27 = 3 3 f (4) = 81 = 3 4 Similarly, f (5) = 3 5 f (6) = 3 6 Thus our series is 3, 3 2 , 3 3 , 3 4 , n terms This is a GP, where a = 3 r = 3 2 3 =3 Given sum of GP = 120 = ( 1) 1 Putting a = 3, r = 3 & sum = 120 120 = 3( 3 1) 3 1 3( 3 1) 2 = 120 3 1 = 120 2 3 3 1 = 40 2 3 = 80 3 = 80 + 1 3 = 80 3 = 3 4 n = 4 n = 4

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo