Home > Just Math
Multi-Logarithms (Posted on 2004-12-08) |
|
If log9(x) = log12(y) = log16(x+y), then find y/x.
|
Submitted by SilverKnight
|
Rating: 3.4000 (5 votes)
|
|
Solution:
|
(Hide)
|
Let: a = log9(x) = log12(y) = log16(x+y)
Then,
16^a = x + y = 9^a + 12^a.
Completing the square, we get:
(3^a + 1/2(4^a))^2 = (5/4)(4^a)^2.
Therefore 3^a = (√5-1)/2)4^a.
Then y/x = 12^a/9^a = 4^a/3^a = 2/(√5-1) = (1+√5)/2 |
Comments: (
You must be logged in to post comments.)
|
|
Please log in:
Forums (0)
Newest Problems
Random Problem
FAQ |
About This Site
Site Statistics
New Comments (3)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On
Chatterbox:
|