Giải phương trình bậc 2 - C/C++

#include <stdio.h>

#include <conio.h>

#include<math.h>

void main()

{printf("*************************************");

    printf("\n GIAI PHUONG TRINH BAC 2");

    printf("\n*************************************");

    float a,b,c,delta;

    printf("\nCho biet he so a = ");

    scanf("%f", &a);

    printf("Cho biet he so b = ");

    scanf("%f", &b);

    printf("Cho biet he so c = ");

    scanf("%f", &c);

    delta = b*b - 4*a*c;

        if (delta < 0)

            printf("Phuong trinh vo nghiem");

                else if (delta == 0)

            printf("Phuong trinh co nghiem kep x1 = x2 = %0.2f", -b/(2*a));

   else{

            printf ("Phuong trinh co 2 nghiem phan biet:\nx1 = %0.2f", (-b + sqrt(delta))/(2*a));

                        printf ("\nx2 = %0.2f", (-b - sqrt(delta))/(2*a));

   }

    printf("\n\nCHUC BAN MOT NGAY TOT LANH.");

    getch();

}