Login

Welcome, Guest. Please login or register.

November 08, 2025, 05:11:50 am

Author Topic: solve x=-ln(x)  (Read 560 times)  Share 

0 Members and 2 Guests are viewing this topic.

Chazef

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 249
  • Respect: +5
  • School: MLMC
solve x=-ln(x)
« on: March 16, 2013, 10:59:51 pm »
0
calculator says that x=0.567143.... and that more solutions may exist. I don't think this is in the course (at least not in the chapter I'm doing) but does anybody know the process for solving something like this?
2012: legal studies [41]
2013: physics [47], chemistry [45], englang [40], softdev [43], methods [44]
ATAR: 99.20
Computer Science @ Monash

pi

  • Honorary Moderator
  • Great Wonder of ATAR Notes
  • *******
  • Posts: 14348
  • Doctor.
  • Respect: +2376
Re: solve x=-ln(x)
« Reply #1 on: March 16, 2013, 11:04:28 pm »
0
Not unless you're familiar with uni concepts such as http://mathworld.wolfram.com/LambertW-Function.html :P

brightsky

  • Victorian
  • ATAR Notes Legend
  • *******
  • Posts: 3136
  • Respect: +200
Re: solve x=-ln(x)
« Reply #2 on: March 16, 2013, 11:07:37 pm »
0
consider the function f(x) = x+ln(x). then compute the numerical approximation using newton's method [you make an initial guess, then find the x-intercept of the tangent line at that point and repeat a gazillion times until you are satisfied with the approximation]. very boring stuff.

you won't be asked to solve transcendental equations in methods.
2020 - 2021: Master of Public Health, The University of Sydney
2017 - 2020: Doctor of Medicine, The University of Melbourne
2014 - 2016: Bachelor of Biomedicine, The University of Melbourne
2013 ATAR: 99.95

Currently selling copies of the VCE Chinese Exam Revision Book and UMEP Maths Exam Revision Book, and accepting students for Maths Methods and Specialist Maths Tutoring in 2020!

Chazef

  • Victorian
  • Forum Obsessive
  • ***
  • Posts: 249
  • Respect: +5
  • School: MLMC
Re: solve x=-ln(x)
« Reply #3 on: March 16, 2013, 11:13:20 pm »
+2
reading stuff like that really makes me appreciate the awesomeness of math, even though I understood almost none of it
EDIT: was referring to that wolfram page
2012: legal studies [41]
2013: physics [47], chemistry [45], englang [40], softdev [43], methods [44]
ATAR: 99.20
Computer Science @ Monash