https://pintia.cn/problem-sets/1105103403392946176/problems/1105103513782833172
#include <stdio.h>
float f(float x);
float a3, a2, a1, a0;
int main()
{
float a, b;
scanf("%f%f%f%f", &a3, &a2, &a1, &a0);
scanf("%f%f", &a, &b);
float left, mid, right;
left = a;
right = b;
while (left <= right - 0.001 && f(left) * f(right) <= 0)
{
if (f(left) == 0)
{
printf("%.2f",&left);
return 0;
}
if (f(right) == 0)
{
printf("%.2f", right);
return 0;
}
mid = (left + right) / 2;
if (f(mid) * f(left) > 0)
{
left = mid;
}
else
{
right = mid;
}
}
printf("%.2f", mid);
return 0;
}
float f(float x)
{
float result;
result = a3*x*x*x + a2*x*x + a1*x + a0;
return result;
}