#include"stdio.h"
#include"math.h"
float f(float x)
{
    return ((x-5)*x+16)*x-80;
}
float xpoint(float x1,float x2)
{
    return (x1*f(x1)-x2*f(x2))/(f(x2)-f(x1));
}
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)
        {
            y=y1;
            x=x1;
        }
        else {x2=x}
    }while(fabs(y)>0.00001)
    return x;
}
main()
{
    float x1,x2,y1,y2,x;
    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("aroot is %f\n",x);
}
帮忙看看哪出错了

写的着急了 呵呵 谢谢提醒啊 ！！！