Kabbalistic Fraction

Algebra Level 3

This fraction extends to infinity. What is the number it approaches?

1 2 \frac {1}{2} e π i { e }^{ \pi i } e e 2 \sqrt { 2 }

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3 solutions

First we evaluate x = 2 + 1 2 + 1 2 + 1 2 + 1 2 + 1 . . . x = 2 + \frac{1}{2 + \frac{1}{2 + \frac{1}{2 + \frac{1}{2+1} ...}}}

x = 2 + 1 x \rightarrow x = 2 + \frac{1}{x}

x 2 = 2 x + 1 x^2 = 2x + 1

x 2 2 x 1 = 0 x^2 - 2x -1 = 0

( x 1 ) 2 2 = 0 (x-1)^2 - 2 = 0

( x 1 2 ) ( x 1 + 2 ) = 0 (x- 1- \sqrt{2})(x - 1 + \sqrt{2}) = 0

x = 1 + 2 , 1 2 x = 1 + \sqrt{2}, 1 - \sqrt{2}

As 1 < 2 1 < \sqrt{2} , this implies that the second root is negative and thus is not a solution.

Therefore x = 1 + 2 x = 1 + \sqrt{2}

The question is asking for x 1 x - 1 , which is equal to 1 + 2 1 = 2 1 + \sqrt{2} - 1 = \boxed{\sqrt{2}}

Nice answer!

Victor Paes Plinio - 7 years, 2 months ago

interesting!

Bezaleel H Prasetyo - 7 years, 2 months ago

Mind blowing!!!!!!

Adarsh Kumar - 7 years, 2 months ago

i did the similar way.............great

Saurav Sharma - 7 years, 2 months ago

interesting

opu lila - 7 years, 1 month ago

Nice Solution :)

JohnDonnie Celestre - 7 years, 1 month ago
Kumar Ashutosh
Apr 13, 2014

The answer is easy to find by looking the options carefully. Since this sum is like 1 + . . . . . . 1 + ...... So it is greater than 1. So 1 2 \frac{1}{2} and e i π e^i\pi . Further, this sum is obviously less than 2 because 1 upon a number greater than 1 is always less than 1. So e e is wrong............... Hence 2 \sqrt{2} is the correct answer.

Much logic 0.o

Joshua Ong - 7 years, 2 months ago

This is way faster than how I did it.

Ahmad Naufal Hakim - 7 years, 2 months ago
Shuchit Khurana
Apr 19, 2014

y-1=1/(2+(y-1)) Game over.

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