BoutCheetah

Other => Off Topic => Topic started by: Racenata on September 01, 2010, 10:19:00 PM

Title: Heh hard one for Allie
Post by: Racenata on September 01, 2010, 10:19:00 PM
"Find x > 3 such that

ln(x) < x^(0.1)"


How do you solve this type of problem? I plugged it into my TI-89 solver and didn't get anything. As a hint, the number is unbelievably huge.
Title: Re: Heh hard one for Allie
Post by: Santa on September 01, 2010, 10:24:48 PM
2^60 = 1,152,921,504,606,846,976

That's one such number, but there are infinitely many more, some smaller and most larger. The proof for x=2^60 is pretty straightforward, though.

First notice that the condition
ln(x) < x^(0.1)
is equivalent to
x < e^( x^(0.1)),
so it is sufficient to show this latter property holds.

Let x = 2^60.
Then x^(0.1) = 2^6 = 64.

Since 2 < e,

2^60 < e^60
< e^64
= e^(2^6)
Title: Re: Heh hard one for Allie
Post by: zomniethe4 on September 01, 2010, 11:08:12 PM
Quote from: RedEyes on September 01, 2010, 10:24:48 PM
2^60 = 1,152,921,504,606,846,976

That's one such number, but there are infinitely many more, some smaller and most larger. The proof for x=2^60 is pretty straightforward, though.

First notice that the condition
ln(x) < x^(0.1)
is equivalent to
x < e^( x^(0.1)),
so it is sufficient to show this latter property holds.

Let x = 2^60.
Then x^(0.1) = 2^6 = 64.

Since 2 < e,

2^60 < e^60
< e^64
= e^(2^6)
My head hurts  :'(
Title: Re: Heh hard one for Allie
Post by: GavinGill on September 01, 2010, 11:18:06 PM
(http://i56.tinypic.com/rhsnrm.png)
Title: Re: Heh hard one for Allie
Post by: Xrow on September 02, 2010, 01:25:44 AM
Quote from: GavinGill on September 01, 2010, 11:18:06 PM
You have a hard one for Allie? What?
HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA.. :3.
Title: Re: Heh hard one for Allie
Post by: S on September 02, 2010, 01:31:46 AM
number is unbelievably huge
Title: Re: Heh hard one for Allie
Post by: Xrow on September 02, 2010, 01:32:28 AM
Quote from: S on September 02, 2010, 01:31:46 AM
number is unbelievably huge

Lol, did you marquee your UB's? o_0
Title: Re: Heh hard one for Allie
Post by: Corr on September 02, 2010, 01:43:43 AM
Quote from: GavinGill on September 01, 2010, 11:18:06 PM
(http://i56.tinypic.com/rhsnrm.png)
This man's a winner.
Title: Re: Heh hard one for Allie
Post by: 7ehNoob on September 02, 2010, 02:41:22 AM
gavin your my hero. i lol'd :D
Title: Re: Heh hard one for Allie
Post by: Yz on September 02, 2010, 05:10:34 AM
the heh ruined whole pic for me, sorry.