Question

求高手，，C语言弦截法方程的根,

#include <math.h>
#include <stdio.h>
float f(float x)
{
return ((x-5)*x+16)*x-80;
}
float xpoint(float x1,float x2)
{
return (x1*f(x2)-x2*f(x1))/(f(x2)-f(x1));
}
float root(float x1,float x2)
{
float x,y,y1,y2;
y1=f(x1);y2=f(x2);
do
{
x=xpoint(x1,x2);
y=f(x);
if(y*y1>0) {y1=y;x1=x;}
else {x2=x;y2=y;}
} while (fabs(y)>0.00001);
return x;
}
void main()
{
float x,x1,x2,y1,y2;
do
{ printf("input x1,x2:");
scanf("%f,%f",&x1,&x2);
y1=f(x1);
y2=f(x2);
} while(y1*y2>0);
x=root(x1,x2);
printf("A root is %f\n",x);
}

Answer 1

#include <math.h>
#include <stdio.h>
float f(float x)
{
float y;
y=((x-5.0)*x+16.0)*x-80.0;
return y;
}

float xpoint(float x1,float x2)
{
float y;
y=(x1*f(x2)-x2*f(x1))/(f(x2)-f(x1));
return y;
}

float root(float x1,float x2)
{
float x,y,y1;
y1=f(x1);
do
{
x=xpoint(x1,x2);
y=f(x);
if(y*y1>0)
{
y1=y;x1=x;
}
else
x2=x;
}while (fabs(y)>=0.00001);
return x;
}

void main()
{
float x,x1,x2,f1,f2;
do
{
printf("input x1,x2:");
scanf("%f,%f",&x1,&x2);
f1=f(x1);
f2=f(x2);
}while(f1*f2>=0);
x=root(x1,x2);
printf("A root is %f\n",x);
}