Calculate Quadratic equation in c language

Simple program to get Quadratic equation in c language

#include< stdio.h> 
#include< math.h> 
int main(){
  float a,b,c;
  float d,root1,root2;   

  printf("Enter a, b and c of quadratic equation: ");
  scanf("%f%f%f",&a,&b,&c);
  d = b * b - 4 * a * c;
  if(d < 0){
    printf("The roots are complex number.\n");
    printf("The roots of quadratic equation are: ");
    printf("%.3f%+.3fi",-b/(2*a),sqrt(-d)/(2*a));
    printf(", %.3f%+.3fi",-b/(2*a),-sqrt(-d)/(2*a));
    return 0; 
  }
   else if(d==0){
   printf("Both the roots are equal.\n");
   root1 = -b /(2* a);
   printf("The root of quadratic equation is: %.3f ",root1);
   return 0;
  }
  else{
   printf("The roots are real numbers.\n");
   root1 = ( -b + sqrt(d)) / (2* a);
   root2 = ( -b - sqrt(d)) / (2* a);
   printf("The roots of quadratic equation are: %.3f , %.3f",root1,root2);
  }
  return 0;
}

Sample output:
Enter a, b and c of quadratic equation: 2 4 1
The roots are real numbers.
The roots of quadratic equation are: -0.293, -1.707