Equation definition from a file:

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

int quad(float a, float b, float c, float *r1, float *r2)
{
float det = b * b - 4.0f * a * c;
if(det < 0.0f)
return 0;
*r1 = (-b + sqrt(det)) / (2.0f * a);
if(det == 0.0f)
return 1;
*r2 = (-b - sqrt(det)) / (2.0f * a);
return 2;
}

void run(float a, float b, float c)
{
float r1, r2;
int num_roots = quad(a, b, c, &r1, &r2);
printf("Function: %.2fx^2 + %.2fx + %.2f\n", a, b, c);
printf("Number of roots: %d\n", num_roots);
if(num_roots == 1)
printf("Root: %.2f\n", r1);
else if(num_roots == 2)
printf("Root 1: %.2f - Root 2: %.2f\n", r1, r2);
}

int main(void)
{
FILE *fp = fopen("test1.txt", "r");
if(!fp) {
return 1;
}
float a, b, c;
int num_read = fscanf(fp, "%f %f %f", &a, &b, &c);
fclose(fp);
return 1;
}
run(a, b, c);
}
```

Several quadratic equations from a file:

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

int quad(float a, float b, float c, float *r1, float *r2)
{
float det = b * b - 4.0f * a * c;
if(det < 0.0f)
return 0;
*r1 = (-b + sqrt(det)) / (2.0f * a);
if(det == 0.0f)
return 1;
*r2 = (-b - sqrt(det)) / (2.0f * a);
return 2;
}

int main(void)
{
FILE *fp = fopen("test.txt", "r");
if(!fp) {
return 1;
}
float largest_root = -1.0f;
float largest_a = -1.0f;
float largest_b = -1.0f;
float largest_c = -1.0f;
for(int i = 0; i < 10000; i++) {
float a;
float b;
float c;
int num_read = fscanf(fp, "%f %f %f", &a, &b, &c);
fclose(fp);
return 1;
}
float r1, r2;
int num_roots = quad(a, b, c, &r1, &r2);
if(num_roots == 2) {
if(r2 > largest_root) {
largest_root = r2;
largest_a = a;
largest_b = b;
largest_c = c;
}
}
if(num_roots != 0) {
if(r1 > largest_root) {
largest_root = r1;
largest_a = a;
largest_b = b;
largest_c = c;
}
}
}
fclose(fp);
printf("Largest root is %.2f. The function is (%.3f, %.3f, %.3f).\n",
largest_root, largest_a, largest_b, largest_c);
}
```