After posting this problem I used some of my time on solutions to equations of logarithms and I found the result as follows:
The system of equation (given below)
logb1w=a1
logb2w=a2
logb3w=a3
.
.
.
logbnw=an
logb1b2b3...bn−1bnbn+1w=an+1
Then,
logbn+1w=1−an+1∑s=1nas1an+1
This is only if w=0
Proof:
From the system of equation (given below)
logb1w=a1
logb2w=a2
logb3w=a3
.
.
.
logbnw=an
logb1b2b3...bn−1bnbn+1w=an+1
We get
b1a1=w
b2a2=w
b3a3=w
.
.
.
bnan=w
(b1b2b3...bnbn+1)an+1=w
Simplifying above expression
b1an+1b2an+1b3an+1...bnan+1bn+1an+1=w
(b1a1)a1an+1(b2a2)a2an+1(b3a3)a3an+1...(bnan)anan+1(bn+1)an+1=w
(w)a1an+1(w)a2an+1(w)a3an+1...(w)anan+1(bn+1)an+1=w
wa1an+1+a2an+1+a3an+1...anan+1bn+1an+1=w
wan+1(a11+a21+a31...an1)bn+1an+1=w
wan+1∑s=1nas1bn+1an+1=w
bn+1an+1=wan+1∑s=1nas1w
bn+1an+1=w1−an+1∑s=1nas1
Taking power 1−an+1∑s=1nas11 on both sides
bn+11−an+1∑s=1nas1an+1=w1−an+1∑s=1nas11−an+1∑s=1nas1=w
Taking logbn+1 on both side
logbn+1w=1−an+1∑s=1nas1an+1
#Algebra
Easy Math Editor
This discussion board is a place to discuss our Daily Challenges and the math and science related to those challenges. Explanations are more than just a solution — they should explain the steps and thinking strategies that you used to obtain the solution. Comments should further the discussion of math and science.
When posting on Brilliant:
*italics*
or_italics_
**bold**
or__bold__
paragraph 1
paragraph 2
[example link](https://brilliant.org)
> This is a quote
\(
...\)
or\[
...\]
to ensure proper formatting.2 \times 3
2^{34}
a_{i-1}
\frac{2}{3}
\sqrt{2}
\sum_{i=1}^3
\sin \theta
\boxed{123}
Comments
@Zakir Husain, please post more PRMO problems. Thank you!
Log in to reply
Got to agree with you!
Neat substitutions! Nice!