All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars    
perplexus dot info

Home > Numbers
Microscopically small (Posted on 2020-11-17) Difficulty: 3 of 5
Find the smallest positive integer n for which 0 < n1/4 - [n1/4] < 10-5.

No Solution Yet Submitted by Danish Ahmed Khan    
No Rating

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution Solution | Comment 1 of 2
Clearly the expression in the middle equals zero if n is a 4th power and will increase until n is the next power of 4.  So were looking for n to be 1 more than a power of 4: n=x^4+1 for whole number x.
This substitution gives us
(x4 + 1)1/4 - 1
A quick table shows the first value of x to be 30, which yields 9.26*10^-6

So the solution is n=30^4+1=810001

(It may be possible to avoid a table with some calculus.)


Edited on November 17, 2020, 10:48 am
  Posted by Jer on 2020-11-17 10:35:13

Please log in:
Login:
Password:
Remember me:
Sign up! | Forgot password


Search:
Search body:
Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (15)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:
Copyright © 2002 - 2024 by Animus Pactum Consulting. All rights reserved. Privacy Information