Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie

How to use the Newton Rapson method to approximate a root ?

Options
  • 23-03-2015 4:56am
    #1
    Captain Hman
    Closed Accounts Posts: 153 ✭✭


    Taking 1.5 as an initial approximation for the root of :

    x^3 - 2x^2 - 3x + 5 = 0

    use the use the Newton Rapson method to approximate a root using 3 iterations


    Can anyone explain to me on how to do this question step by step please ?


Comments

  • Options
    #2
    Michael Collins
    Moderators, Science, Health & Environment Moderators Posts: 1,847 Mod ✭✭✭✭Michael Collins


    Well the first thing would be to find the Netwon-Ralphson iteration formula. Usually written something like

    [latex] x^{(n+1)} = x^{(n)} - \cdots [/latex]

    If you reply with this we can go from there.


  • Options
    #3
    Yakuza
    Registered Users Posts: 5,141 ✭✭✭Yakuza


    Take a look here: http://en.wikipedia.org/wiki/Newton's_method

    I've done it, it converges quite well after 3 iterations using an initial guess of 1.
    You'll need a PC with Excel or a programming language to work it out accurately (after the second iteration using a calculator will get fiddly).

    As MC says, post up what you've tried so far and we'll give you some more pointers / feedback.


Advertisement