C programs not working..:-(

[puter_nerd]

Im writing a program to find the root of the sixth degree equation f(x) = x^6 - 10x^5 - 38x^4 + 368x^3 + 445x^2 - 2950x -3000

but it keeps giving me a floating exception...:-(
Can nyone help!!!!!!?????

#include<stdio.h>
#include<stdlib.h>
int main(int argc, char *argv[])
{
float new_guess;
float last_guess;
new_guess=9;
do
{
last_guess=new_guess;
new_guess = last_guess - f(last_guess)/fprime(last_guess);
printf("Guess: %f\n",new_guess);
}while(abs(new_guess - last_guess) > 0.01);
printf("Root of the sixth degree equation is: %f\n",new_guess);
return EXIT_SUCCESS;
}

float f(float x)
{
float y;
y= x*x*x*x*x*x - 10*(x*x*x*x*x) - 38*(x*x*x*x) + 368*(x*x*x) + 445*(x*x) - 2950*x -3000;
return y;
}
float fprime(float x)
{
float z;
z= 6*(x*x*x*x*x) - 50*(x*x*x*x) - 152*(x*x*x) + 1140*(x*x) + 890*x -2950;
return z;
}

[dragonB]

I cut and pasted ur program, compiled it using Borland's free compiler and it ran fine.

here's what I get...


Guess: 11.617638
Guess: 10.730997
Root of the sixth degree equation is: 10.730997


so, not sure what ur problem is.
Oh, I did move the function definitions in front of the main program, but I think that's just cuz this compiler is picky, and didn't see them.
good luck

[puter_nerd]

yes it does give that value when i move teh functions to teh front of main but the value is still incorrect
i tried teh program with a smaller equation like x^2-3x+2 and it gives wrong result..
cant figure put wht the problem is..
Thanx a heap for ure help


float f(float x)
{
float y;
y= x*x*x*x*x*x - 10*(x*x*x*x*x) - 38*(x*x*x*x) +368*x*x*x) + 445*(x*x) - 2950*x -3000;
return y;
}
float fprime(float x)
{
float z;
z= 6*(x*x*x*x*x) - 50*(x*x*x*x) - 152*(x*x*x) + 1140*(x*x) + 890*x -2950;
return z;
}

int main(int argc, char *argv[])
{
float new_guess;
float last_guess;
new_guess=1;
do
{
last_guess=new_guess;
new_guess = last_guess - f(last_guess)/fprime(last_guess);//relation to calculate result
printf("Last Guess: %f\n",last_guess);//prints the last guess
printf("New Guess: %f\n",new_guess);/*primnts teh calculated value of new guess*/
printf("f=:%f\n",f(new_guess));//prints value of f(x)
printf("fprime=:%f\n",fprime(new_guess));/*prints value of fprime(x)*/
}while(abs(new_guess - last_guess) > 0.01);//condiiton for loop
printf("Root of the sixth degree equation is: %f\n",new_guess);
printf("%f\n",f(new_guess)); /*if root evaluated correctly this should be almost zero*/
return EXIT_SUCCESS;
}

[strangerstill]

Well, to start with, d/dx(368x³) = 1104x² not 1140x²

[strangerstill]

Also you seem to have misplaced a bracket in f()

[strangerstill]

Also, when posting code, could you use the [CODE] tag (the # button above)?

It makes it a lot easier to read as it doesn't break lines & it keeps tabs.

Thanks

Tell me if the above stuff helped.

[puter_nerd]

hi stranger and dragon...thanx again for all ure help..this one is still giving me problems
even after correcting the values i still cant get it to give me the correct result.Must be somethign to do with the logic
Ny suggesstions
Thanx again

[strangerstill]

Your maths looks OK... I get -3 as the answer, which works.

[puter_nerd]

yes it is...stupid me
thanx