Magic of Math#2

Algebra Level 1


The answer is 0.

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2 solutions

Francesco Grechi
Aug 25, 2015

I have some questions about this question.

To start solving this question, I began by defining 1 = x \clubsuit_1\ = x , for purely simplification reasons. I then observed that:

1 = x \clubsuit_1=x

2 = 1 + 1 = 2 1 \clubsuit_2=\clubsuit_1 + \clubsuit_1= 2\clubsuit_1

3 = 2 + 1 + x = 2 + 2 = 2 2 \clubsuit_3=\clubsuit_2 +\clubsuit_1 + x=\clubsuit_2+\clubsuit_2= 2\clubsuit_2

\vdots

(1) n = 2 n 1 \clubsuit_n= 2\clubsuit_{n-1} , where n is a natural number s.t. n ( 1 , ) n \in (1, \infty)

I then came to a metaphorical fork in the road. I was not certain whether the problem wanted (1) to be simplified in the form:

(2) n = 2 n + 1 1 \clubsuit_n = 2^{n+1}\clubsuit_1 , or not

Equation (2) can be obtained by observing the pattern of the equations obtained by substituting each occurrence of n 1 \clubsuit_{n-1} with twice the previous term, ad infintum .

Although both (1) and (2) are equal, they would have very different conclusions as to the solution of the question. (1) would imply that:

k b = lim b 2 b = 0 \lfloor \frac{k}{b} \rfloor =\lim_{b \to \infty} \lfloor \frac{2}{b} \rfloor = 0 , which is the answer that was set as correct.

However (2) would imply that:

k b = lim n 2 n + 1 n 1 \lfloor \frac{k}{b} \rfloor = \lim_{n \to \infty} \lfloor \frac{2^{n+1}}{n-1} \rfloor , which can be shown through the ratio test to be equal to lim k k = \lim_{k \to \infty} \lfloor k \rfloor = \infty . Therefore the answer to the question is \infty . This answer is somewhat different.

I guess my main difficulty resides in the lack of specification of b. Is the question asking for b, s.t. b is a finite number or not?

OK! I give up there are two answer.But I think you don't have infinity symbol on your keyboard!

Magic Math - 5 years, 9 months ago

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So your question is not cleaver enough

Porames Vattanaprasan - 5 years, 9 months ago

If Diamond = X ('cause I can't type it :P) X(infinite)=(infinite-1)X(infinite) Floor k/b = Floor (infinie-1)/infinite = 0 Is that correct?

Why are you asking me? Just answer it!

Magic Math - 5 years, 9 months ago

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I've answered it already So I can discuss the solution here lol

Porames Vattanaprasan - 5 years, 9 months ago

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