[Show all top banners]

tregor
Replies to this thread:

More by tregor
What people are reading
Subscribers
:: Subscribe
Back to: Kurakani General Refresh page to view new replies
 solve this equation

[Please view other pages to see the rest of the postings. Total posts: 63]
PAGE: <<  1 2 3 4  
[VIEWED 18158 TIMES]
SAVE! for ease of future access.
The postings in this thread span 4 pages, go to PAGE 1.

This page is only showing last 20 replies
Posted on 03-01-06 1:15 PM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

can anyone solve: x^2 - 2^x =0 by algebraic method???
(x squared minus two to the power x equals zero)
of course, without using graphing calculator.
 
The postings in this thread span 4 pages, go to PAGE 1.

This page is only showing last 20 replies
Posted on 03-03-06 11:28 PM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

this is a very very intriguing problem
 
Posted on 03-04-06 12:32 AM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

@crisna hehe
see for example lets consider a general case
2^a-a^2=0
now here 'a' could be complex or
a could be so huge that your computer cannot handle
the calculation then you need analytical method. Fortunately
the analytical method seems to exist . See my previous post.
 
Posted on 03-04-06 10:46 AM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

Lambert's W function........yes absolutely.......i am used to the term "product log" but ... it's the same thing. i have seen people using product log to solve these kinda problems.......
I have just finished my calc 1 so m dunno much abt using product log......but guess someone who have used it can solve the equation.....this certainly is not in my course but it's my curosity to get the way....

one of my cousins has half completed it by product log (Lambert's function)
divdude,you are likely to make it
 
Posted on 03-04-06 11:19 AM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

Hey dude,
Solving in tems of a Lamberts function is not an analytical solution. If you get the answer in terms of a Lamberts function, you then have to solve the Lamberts function numerically agian.
Let me explain why you cannot get an absolute analytical solution of that equaiton. To solve that equation one should be able to collect x in a place. You just cannot do it if you have log(x) or e^x or 2^x and x together i none equation. Why? because for example log(1+x)=x-x^2/2+x^3/3........and similar expansions for e^x and 2^x.
It is impossible to extract x analytically to solve it analytically. You have to use some function like Lamberts or solve it numerically.

Hope I made my point clear.

Implementation of this in Matlab is easy.
 
Posted on 03-04-06 11:53 AM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

kasto garo...

x^2 - 2^x = 0
or, x^2 = 2^x
or lgx^2 = lg2^x
or 2lgx = xlg2
or x/lgx = 2/lg2
therefore, x = 2; however, x/lgx = 2/lg2 can also be expressed as:
(2*2)/(2*lg2) (multiplying by 2/2=1)
=4/(lg2^2)
= 4/lg4
Giving x = 4.

Result: x = (2,4)

khoi k ho k ho....hisab bhanney pachi aafu lai pisab aaucha
 
Posted on 03-04-06 12:07 PM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

Hey Chris,
this is again not an analytical solution, what the original poster is looking for an analytical solution, that is, a way to solve algebraically,
What you doing is putting x=2 and x=4, to make the equaiotn satisfied. If you dont know the answer(for eample in a complex version of the equation, your method of trial and guess wont work.
I still insist every body not to look for abstract analyticcal solution, its just not possible.
The best way to solve it is numerically or graphically
 
Posted on 03-04-06 12:15 PM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

I think I need my eyes checked. I read original poster posting," Can anyone solve: x^2 - 2^x =0 by algebraic method??? " :-s
 
Posted on 03-04-06 12:25 PM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

Yea you indeed need to check your eyes,
Thats why you should do it algebraically and not by trail and error method!
 
Posted on 03-04-06 12:42 PM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

J method bhaye ni baal ho; answer aaye pugyo. :D
khoi class 8 padha algebra bhannya x , y patta lagauney bhanthiye...advance bhayecha ajkal...k k method k k method, kehi bujhey ta mori jaam ;-)
 
Posted on 03-04-06 3:30 PM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

thanks chirscornell
eeveryone was able to get the step logx/x=log2/2..........and conlude x=2 which i was not looking for
but multiplying by 2/2 to get x=4 was good ....its kinda hit n trial but still appreciable.........
 
Posted on 03-06-06 1:24 AM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

any more comments?
 
Posted on 03-06-06 2:28 AM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

@crisna
I dont know much about lamebrt W function but it
does have a proper algebrical expression. So getting
solution in terms of Lamberts W function is equivalent to
getting results in algebric form.
For instance it is okay if we get result in log but to calculate
actual log value you sitll have to get the value numerically.
So I cant see why cant the solution of equation be expressed
in Lamebrt's w function.
 
Posted on 03-06-06 8:59 AM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

` even if we take this Lambert function, we have to realize something - we lose information when we take logs. possible negative (and thus imaginary and complex) solutions are supressed as soon as the original equation is expressed in terms of logs. see the above graphs in previous posts.
 
Posted on 03-06-06 5:13 PM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

the graphs only show the real solutions.............
 
Posted on 03-06-06 8:24 PM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

I did a little study on Lambert w function. Lambert w
function is actually a complex function and can also
be expressed in form of laurant series.
And it is multivalued i.e there are multiple solutions in
complex plane but only 3 solutions in real line. About
log i am not exactly sure but to say the least i remember
this equation from Isc 2nd year,
logx=x+x^2/1!+x^3/2!+.........
so basically value of log can be found with good degree of precision.
And you also can take log for complex numbers.
But log being 200year old tradition, I dont really think
it has too many flaws.
 
Posted on 03-07-06 10:39 AM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

` you're right tregor. i still wonder why is it that the negative soln. is lost when we take logs.
 
Posted on 03-07-06 11:04 AM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

You cannot take log of negative number but
log of a value can have negative number
 
Posted on 03-07-06 11:12 AM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

Ah damm i forgot one small relation that i studied in complex analysis.
Damm my memory.
ok
log(-1)=plus or minus i*PI
 
Posted on 03-07-06 2:58 PM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

can u elaborate?
 
Posted on 03-07-06 4:13 PM     Reply [Subscribe]
Login in to Rate this Post:     0       ?    
 

i don't think you can have log(-x), because this is base 10. for x to be -tive, the base must be and has to be an odd number.
 



PAGE: <<  1 2 3 4  
Please Log in! to be able to reply! If you don't have a login, please register here.

YOU CAN ALSO



IN ORDER TO POST!




Within last 90 days
Recommended Popular Threads Controvertial Threads
TPS Re-registration case still pending ..
Toilet paper or water?
From Trump “I will revoke TPS, and deport them back to their country.”
Tourist Visa - Seeking Suggestions and Guidance
advanced parole
Sajha Poll: Who is your favorite Nepali actress?
ढ्याउ गर्दा दसैँको खसी गनाउच
To Sajha admin
Problems of Nepalese students in US
अरुणिमाले दोस्रो पोई भेट्टाइछिन्
Mamta kafle bhatt is still missing
Nepali Passport Renewal
seriously, when applying for tech jobs in TPS, what you guys say when they ask if you have green card?
Are Nepalese cheapstakes?
Nepali Psycho
MAGA denaturalization proposal!!
How to Retrieve a Copy of Domestic Violence Complaint???
wanna be ruled by stupid or an Idiot ?
NOTE: The opinions here represent the opinions of the individual posters, and not of Sajha.com. It is not possible for sajha.com to monitor all the postings, since sajha.com merely seeks to provide a cyber location for discussing ideas and concerns related to Nepal and the Nepalis. Please send an email to admin@sajha.com using a valid email address if you want any posting to be considered for deletion. Your request will be handled on a one to one basis. Sajha.com is a service please don't abuse it. - Thanks.

Sajha.com Privacy Policy

Like us in Facebook!

↑ Back to Top
free counters