Just a second...

A sequence is defined as a1 = a2 = 1 and an = an-1 + an-2 for all n ≥ 3 then

{ an } is an increasing sequence TRUE / FALSE

5 Answers

106
Asish Mahapatra ·

This is Fibonacci sequence .. the terms are increasing
1,1,2,3,5,8,13,21,....

proof:

all terms are positive..
an > an-1 (as all terms are positive and an = a(n-1) + a(n-2) )

=> the next term is greater than the previous term hence the sequence is increasing

341
Hari Shankar ·

Its like this, they want you to prove that every term is +ve which is easily done by strong induction

106
Asish Mahapatra ·

sir as any term is the sum of its previous terms..
and the first two terms are positive .. then wont all terms be positive..

(as it is given true/false question) i did not bother about induction..

But sir isnt this a bit too obvious for induction (i mean it is clearly the fibonacci series isnt it)?

341
Hari Shankar ·

Ya, the qn is ill-framed that way. The idea is to argue from fundamentals rather than from known facts. But using the Fibonacci recursion is bad judgement from the question setter.

62
Lokesh Verma ·

@Prophet Sir: I wonder how many ppl i know understand "mathematics" as well as you do [1]

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