Ask Experts Questions for FREE Help !
Ask
    scantor145's Avatar
    scantor145 Posts: 2, Reputation: 1
    New Member
     
    #1

    Nov 7, 2008, 04:50 AM
    solve an equation with ln x
    How do you solve the following:

    y = x + ln x
    ebaines's Avatar
    ebaines Posts: 12,131, Reputation: 1307
    Expert
     
    #2

    Nov 7, 2008, 06:50 AM

    What do you mean by "solve?" Are you asking if there's a way to solve for x given a value for y? Or do you mean you want to find the root(s) of this equation (i.e. for y = 0)?
    Capuchin's Avatar
    Capuchin Posts: 5,255, Reputation: 656
    Uber Member
     
    #3

    Nov 7, 2008, 06:57 AM

    Indeed, I would say it's already solved for y ;)
    scantor145's Avatar
    scantor145 Posts: 2, Reputation: 1
    New Member
     
    #4

    Nov 7, 2008, 07:13 AM
    Quote Originally Posted by ebaines View Post
    What do you mean by "solve?" Are you asking if there's a way to solve for x given a value for y? Or do you mean you want to find the root(s) of this equation (i.e., for y = 0)?

    I want to solve for x, as in x + ln x = 10.
    I believe I've found out that one needs to use Newton's method to get a very close approximation. I think that the Solver add-in in Excel will do the trick.

    I've also heard that a function, Lambert W, will solve it exactly.
    ebaines's Avatar
    ebaines Posts: 12,131, Reputation: 1307
    Expert
     
    #5

    Nov 7, 2008, 07:23 AM

    With the exception of obvious solutions such as x + ln(x) = 1, I don't know of a closed form solution for this, so using an approximation technique like Newton's method is a good approach.

Not your question? Ask your question View similar questions

 

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

What equation do I use to solve this? [ 2 Answers ]

An elevator weighing 20000 N is supported by a steel cable. What tension is the cable when the elevator is being accelerated upward at a rate of 3.00 m/s

Solve equation [ 3 Answers ]

X-7 = -2

Solve equation [ 3 Answers ]

x-7=-2

Solve the equation [ 1 Answers ]

|(cot^2)2x + 8 sqrt(-cot2x) - 3|=|(cot^2)2x - 8 sqrt(-cot2x) - 3|

To solve an equation [ 13 Answers ]

How can I solve this equation? a raised to 4.10667 = e raised to a. e is number e. I know a is 9.0427 (only 4 decimals). Is there a method? Thanks


View more questions Search