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C program to find roots of a quadratic equation

Quadratic equation
C program to find roots of a quadratic equation: Coefficients are assumed to be integers, but roots may or may not be real.

For a quadratic equation ax2+ bx + c = 0 (a≠0), discriminant (b2-4ac) decides the nature of roots. If it's less than zero, the roots are imaginary, or if it's greater than zero, roots are real. If it's zero, the roots are equal.

For a quadratic equation sum of its roots = -b/a and product of its roots = c/a. Let's write the program now.

Roots of a Quadratic equation in C

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

int main()
  int a, b, c, d;
  double root1, root2;

  printf("Enter a, b and c where a*x*x + b*x + c = 0\n");
  scanf("%d%d%d", &a, &b, &c);

  d = b*b - 4*a*c;

  if (d < 0) { // complex roots, i is for iota (√-1, square root of -1)
    printf("First root = %.2lf + i%.2lf\n", -b/(double)(2*a), sqrt(-d)/(2*a));
    printf("Second root = %.2lf - i%.2lf\n", -b/(double)(2*a), sqrt(-d)/(2*a));
  else { // real roots
    root1 = (-b + sqrt(d))/(2*a);
    root2 = (-b - sqrt(d))/(2*a);

    printf("First root = %.2lf\n", root1);
    printf("Second root = %.2lf\n", root2);

  return 0;

Output of program: 
Quadratic equation program output