Math Is Fun Forum

purev1olence

Member

Registered: 2008-06-03

Posts: 1

Need help on my JS Quintic Equation Calculator

I need help on my Quintic Equation Calculator. It uses the Netwon-Raphson method to approxmate the root and I have mainly got this all right. But heres the deal, sometimes the guess is real far away and I cant get it to converge quick enough, although I can press the Solve button again and it gives me the right answer. I have also noticed that sometimes it takes >5,000 tries before the answer converges. Can anyone help me find a new intial guess algorithm that will converge within 5,000 iterations? Thanks.

- Brian K

Quintic Equation Calculator: http://www.freewebs.com/brianjs/quinticequationcalculator.htm

Ricky

Moderator

Registered: 2005-12-04

Posts: 3,791

Re: Need help on my JS Quintic Equation Calculator

You could use the value at a random point an it's derivative to find which direction on the complex plain will get you closer to 0.  Iterate over this with step sizes based upon the magnitude of the value and derivative will help to ensure you don't accidentally step over any.

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"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

purev1olence

Member

Registered: 2008-06-03

Posts: 1

Re: Need help on my JS Quintic Equation Calculator

Thansk, but I dont understand :\ im only 14