/tmp/ccFbD8lA.o: In function `main':  
/tmp/ccFbD8lA.o(.text+0x9d): undefined reference to `sqrt'
collect2: ld returned 1 exit status

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

int main()
{
        int a, b, c, a2;
        float x1, x2, part1;


        printf("A: ");
        scanf("%d", &a);
        printf("B: ");
        scanf("%d", &b);
        printf("C: ");
        scanf("%d", &c);

        part1 = sqrt( (b*b) - 4*a*c);
        a2 = 2*a;
        printf("-b = %d\nB^2 - 4AC = %f\n2A = %d.\n", -b, part1, a2);

        x1 = ((-b) + part1) / (2*a);
        x2 = ((-b) - part1) / (2*a);

        printf("X = %f\nX = %f", x1, x2);
        return 0;
}