Math Problem

Question

I need some help! I admit, I'm not a java guru...far from it, just a college student with a book that doesn't have many examples for what I'm looking for. Any help will be greatly appreciated!!!
My problem: My java program is to find a root using the Newton-Rapson method. The input is a function, i.e. f(x) = x^2 + x + 2. The program is to prompt the user for the beginning numbers, i.e. 225 and -43, and then find the answer to the nearest hundredth.
I can do this on paper - no problem, my problem is I don't know enough about Java to program it to do the math.
Unfortunately, if there are any predefined classes or methods that will do this problem for me, I'm NOT allowed to use them. Every step has to be hard coded. :(
I'm not sure how to get Java to recognize the + sign or
the ^ sign or any other non-numeric signs. I know there is something called substring, but I can't seem to find examples where it uses an integer. All the examples I have found are chars (like reading the string "hello"). Not helpful when you are trying to mix integers with symbols.
Any help offered would be greatly appreciated, and I'm sure would in-turn help me the the bisection algorithm and all the future algorithm's I have to put into a program.
Thanks for your time.

Answer 1

[mode=Pedantic] Its Newton-Raphson [mode]
Anyway use this as a starting point, its from a guy by the name of Neil Broadbent (see: http://www.neiljohan.com/java/ for lots of java samples)
This will calculate the square root of a number using Newton-Raphson factoring, you can use this as a starting point.
//Program to calculate the square root of a number using the Newton-Raphson.
//It stops when the difference between consecutive approximations is less than 0.00005
//by Neil Broadbent
import java.io.IOException;
import NeilClass.*;
public class NewtonRaphsonClass
     private static boolean debugging = true;
     /** @param tFactorial the value from which to find the square root
      *  precondition tFactorial>0
      *  @return x1 so that x1>0 */
    public static double iSquareRoot (double tFactorial) throws IOException
            double x1=0;
            double x0=tFactorial/2;
            double a=tFactorial;
            boolean finished=false;
     /* check pre-condition */
     if (debugging && (tFactorial<=0)){
          System.out.println("Pre-condition violoated");
          finished=true;
            while (finished==false)
                x1=(x0+(a/x0))/2;
                if (x1>x0){
                    if ((x1-x0)<0.00005){
                        finished=true;
                else if (x0>x1){
                    if ((x0-x1)<0.00005){
                        finished=true;
                x0=x1;
          /* check post-condition */
          if (debugging && (x1<=0)){
               System.out.println("Post-condition violoated");
            return x1;
}