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

Home > Numbers
Gold in the Exponent (Posted on 2019-12-11) Difficulty: 3 of 5
What real value of x satisfies the equation 9^x + 12^x = 16^x?

See The Solution Submitted by Brian Smith    
Rating: 4.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution Explanation to Puzzle Answer Comment 6 of 6 |
(In reply to Puzzle Answer by K Sengupta)

Dividing both sides by 9^x, we have:

1 +(4/3)^x =(16/9)^x
Then, substituting n= (4/3)^x, we must have:
1+n=n^2 => n^2 - n -1 = 0
=> n = (1+/-V5)/2
If n=(1-V5)/2, then n must be < 0 as V5>1
In that situation, (4/3)^x will give us:
x*log(4/3) as a non-real quantity. Contradiction. 
Accordingly,  we must have n ={(1+V5)/2}
Then, x*log(4/3) = log{(1+V5)/2 }
=> x ~=  (0.8089876402)/(0.1249387366)
~= 1.67272

Edited on May 29, 2022, 11:01 pm
  Posted by K Sengupta on 2022-05-29 23:01:23

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 (6)
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