Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: √ ∞ ≠ ≤ ≥ ≈ ⇒ ∈ Δ θ ∴ ∑ ∫ π -

Login

Username

Password

Not registered yet?

Post a reply

Go back

Write your message and submit
:) :| :( :D :o ;) :/ :P :lol: :mad: :rolleyes: :cool: | :dizzy :eek :kiss :roflol :rolleyes :shame :down :up :touched :sleep :wave :swear :tongue :what :faint :dunno
Options

Go back

Topic review (newest first)

Ricky
2005-12-22 02:10:51

Maybe he just has the midas touch.

John E. Franklin
2005-12-21 15:29:33

I don't know why, but in post #2 by ryos, the golden ratio
shows up twice.   (√(5) - 1)/2)  and 1.61803

Ricky
2005-12-15 21:25:25

would not b / a = (4 / 3)^x be a suitable answer?

Ricky
2005-12-15 21:20:27

Yea, that is quite an equation, I don't believe I've ever had to solve one like it before.

My calculator comes up with 9^x = 16^(ln(3)x / 2*ln(2)) and 12^x = 16^(ln(12)x/4*ln(2))

This makes the equation:

16^x = 16^(ln(3)x / 2*ln(2)) + 16^(ln(12)x/4*ln(2))

That seems to be a step in the right direction, getting a common base.  And can anyone derive 9^x = 16^... and 12^x = 16^....?

ryos
2005-12-15 18:17:56

First rewrite them in exponential form:

9^x = a
12^x = b
16^x = a + b    16^x = 9^x + 12^x
Solve for x.

You know, I'm not sure that's even possible without the aid of technology. My calculator says that:
x = ln[ (√(5) - 1)/2) ] / ln(3/4).
That's log base 3/4 of (√(5) - 1)/2), which is 1.67272.

Guess what? 12^1.67272 / 9^1.67272  =  63851199804262/39462211701495.  More sanely, it = 1.61803.

Anyone who can solve 16^x = 9^x + 12^x for x by hand deserves a trophy.

MajikWaffle
2005-12-15 16:17:15

http://img228.imageshack.us/img228/1799/untitled8av.png

can someone explain this to me?

Board footer

Powered by FluxBB