#include <stdio.h>
#include <math.h> 

float f(float x) 
{ 
float y; 
y=0.002*9.81-1.4*(1/10*10*10*10*10)*sqrt(x*x*x)-1.5*(1/10*10*10*10*10)*x*x ;
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) 
{ 
int i; 
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)>=0.0001); 
return (x); 
} 


main() 
{ 
float x1,x2,f1,f2,x; 
do 
{ 
printf("input x1,x2:\n"); 
scanf("%f,%f",&x1,&x2); 
f1=f(x1);f2=f(x2); 
}
while(f1*f2>=0); 
x=root(x1,x2); 
printf("A root of equation is %8.4f\n",x); 
} 


 -1.#IND