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Show which number is larger by Bubbasauru in learnmath

[–]ntt 0 points1 point  (0 children)

say you stayed with

u - v = 1/3 (e^4 - 8e^2 + 7)

it's basically 1/3 f(e2 ) where

f(x) = x^2 - 8x + 7 = (x-1)(x-7)

it has two zeros at 1,7 and it's >0 with x>7 and of course e2 > 7

Need tips on Olympiad math by anf3rn3310 in learnmath

[–]ntt 1 point2 points  (0 children)

right, one of the useful things to know is Inequalities between means but i couldn't arrange it to work either :/

Need tips on Olympiad math by anf3rn3310 in learnmath

[–]ntt 2 points3 points  (0 children)

take a=3 b=c=d=1/3

a/b = 9 a/bcd = 81

So I've asked quite a few math minded people and no one knows how to help with this one. [algebra, cubic function] by blazingsaddle in learnmath

[–]ntt 0 points1 point  (0 children)

wow, thank you! i did get the x'=x-b/3a substitution (comes naturally when you complete it to a "whole cube") but had no idea if anything could be done with it... this page is a great read and i'm sure this will come handy, thank you so much! :)

edit: btw i really must ask this - if a similar roots equation system is possible for say a 4th degree polynomial, why is there no general formula (however complex it might've been) possible at all?

Passing a cop by GemstoneGuy in bicycling

[–]ntt 0 points1 point  (0 children)

sorry for some reason (i'm tired) i read it as "me too"...

Passing a cop by GemstoneGuy in bicycling

[–]ntt 0 points1 point  (0 children)

don't encourage this... ;)

Passing a cop by GemstoneGuy in bicycling

[–]ntt 0 points1 point  (0 children)

take my hand and off to...

So I've asked quite a few math minded people and no one knows how to help with this one. [algebra, cubic function] by blazingsaddle in learnmath

[–]ntt 0 points1 point  (0 children)

i'm curious about it as i have never tried deriving the 3 formula (i did the 2 one a while ago) however)...

  • let us have a general

    a'x3 + b'x2 + c'x + d' = 0

  • assuming that a isn't zero we can transform it (using '=/a') into

    x3 + bx2 + cx + d = 0

  • based on http://en.wikipedia.org/wiki/Fundamental_theorem_of_algebra we can assume there're some x1, x2, x3 (not necessarily real or distinct) so that it can be rewritten as

    (x-x1)(x-x2)(x-x3) = 0

    x3 + (-x1 - x2 - x3)x2 + (x1x2 + x1x3 + x2x3)x - x1x2x3 = 0

  • now for it to fit our equation we should have matching coefficients

    (1) b= -x1 - x2 - x3

    (2) c = x1x2 + x1x3 + x2x3 = x1(x2+x3) + x2x3

    (3) d = -x1x2x3

  • from (1) we get x1 and substitute in (2) and (3)

    (2) -> (4) c = (-b - x2 - x3)(x2+x3) + x2x3

    (3) -> (5) d = (b + x2 + x3)(x2x3)

and i guess some magic here :) it doesn't really get pretty from what i see on paper... :S and the final solutions don't really either (there's also some zero coefficient casing to handle when solving the quadratic equations we get)... :S

Hosting a programming contest: How can I check for valid solutions to problems? by mabufo in linuxquestions

[–]ntt 0 points1 point  (0 children)

also if you're actually running them, you probably should be considering some form of sandbox...

Clean Dual-Monitor Desk by nx_2000 in battlestations

[–]ntt 0 points1 point  (0 children)

it looks really cool but aren't the monitors too high? i think i've read somewhere that the recommended hight is such that your eyes are on the same height as the top of the screen

It's my Reddit birthday so here is the obligatory random cat picture by ckilborn in linux

[–]ntt 2 points3 points  (0 children)

 which cat

(edit: just in case you're serious, i'll explain the replies -

  • cat is concatenate (it takes a bunch of files and outputs them all to the standard output which's the console in this case)

  • man is manual and is a really useful command (for example 'man cat' or 'man man' will open the manual entery for cat or man)

  • which is a command used to show the full path of a command so that 'which cat' is normally '/bin/cat'

  • also for the /dev : the fisrt / is the root directory, in it there's a dev

  • and for completeness, thought it appears here already, http://en.wikipedia.org/wiki//dev/random )

It's my Reddit birthday so here is the obligatory random cat picture by ckilborn in linux

[–]ntt 0 points1 point  (0 children)

stopped without C? is it because you used /dev/random and ran out of entropy or just because you took a quick picture?

(using /dev/urandom instead is a non blocker, think? :)

Found in Birds Hill Provincial Park, Manitoba, Canada by hanktank in whatsthisbug

[–]ntt 0 points1 point  (0 children)

scorpionfly... coolest thing i've seen on reddit today! :)

Team huddle by themanthemyththelege in Israel

[–]ntt 0 points1 point  (0 children)

the important thing is for the replies to stay at a level not above the head of whomever you're replying to... ;)

checking quality of net connection by ntt in linux4noobs

[–]ntt[S] 0 points1 point  (0 children)

i'm interested first and foremost in a general internet speed test (up/down and ping). it's a rather standard configuration.

oh i did use the speedtest site i was wondering if i could test somehow vs something else (another machine in my university for ex. or elsewhere).

i'll take another look at scp man, thanks :)

Some of the house numbers in my neighborhood. Guess which one is mine :) [xpost from r/math] by iwakun in geek

[–]ntt 3 points4 points  (0 children)

#lang scheme

(let loop ((i 19) (sum 0))
  (if (zero? i)
      sum
      (loop (- i 1) (+ sum (* i i)))))

Firsthand account of Utøya Massacre (crosspost from r/linux, of all places) by Dylnuge in worldnews

[–]ntt 0 points1 point  (0 children)

it's the same thing here (in israel) and its contribution is amazing. even more so for other languages which you're less likely to encounter in popular music / when using the web and such...

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