# include <stdio.h>

# include <math.h>

int main (void)

{
    float a;
    float b;
    float c;
    double dalte;
    double x1;
    double x2;
   

  printf ("请输入a,b,c的值：\n");



    scanf("%f,%f,%f",&a,&b,&c);

    dalte = b*b-4*a*c;
   
    if (dalte > 0)
        x1 = ((-b)+sqrt(dalte)) / (2*a);
        x2 = ((-b)-sqrt(dalte)) / (2*a);
    printf("该一元二次方程有两个解：x1 = %f\n, x2 = %f\n",x1, x2);

     else if(dalte == 0)
        x1 = -b/2*a;
        x2 = x1;
    printf ("该一元二次方程有唯一解：x1 = x2 = %f\n",x1);

    else (dalte < 0)
        printf ("该一元二次方程无解\n");





        return 0;
}

想了半天，不知道错在哪里，求教，谢谢

[ 本帖最后由 yujian222000 于 2014-8-28 21:42 编辑 ]

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

int main (void)

{
    int  a ;
    int  b ;
    int  c ;
    double x1;
    double x2;
    double datle;

printf ("请输入a,b,c的值");

    scanf ("%f ,%f, %f",&a,&b,&c);

    datle = b*b-4*a*c;

    if (datle > 0)
    {
        x1 = (-b+sqrt(datle))/2*a;
        x2 = (-b-sqrt(datle))/2*a;
        printf ("该一元二次方程有两个解：x1 = %f,x2 = %f\n",x1,x2);
    }

    else if (datle == 0)
    {   
        x1 = (-b)/2*a;
        x2 = x1;
        printf ("该一元二次方程有唯一解：X1 ＝ x2 = %f\n",x1);
    }
        else
        {
            printf ("该一元二次方程无解\n");
        }



    return 0;
}

请教，程序我改了，加了{}，运行无错，但是输出结果却看不太明白，比如我输入5 4 1，应该是无解的，但是运行结果却是两个垃圾值

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

int main (void)

{
    float  a = 1 ;
    float  b = 14;
    float  c = 3;
    float x1;
    float x2;
    float datle;





    datle = b*b-4*a*c;

    if (datle > 0)
    {
        x1 = (-b+sqrt(datle))/2*a;
        x2 = (-b-sqrt(datle))/2*a;
        printf ("该一元二次方程有两个解：x1 = %f,x2 = %f\n",x1,x2);
    }

    else if (datle == 0)
    {   
        x1 = (-b)/2*a;
        x2 = x1;
        printf ("该一元二次方程有唯一解：X1 ＝ x2 = %f\n",x1);
    }
        else
        {
            printf ("该一元二次方程无解\n");
        }



    return 0;
}


我将程序改成这样，手动输入abc的值就没有问题，加上scanf后就不行了，看来是scanf函数没学好，谢谢各位大侠的指导

谢了，我是新手，刚开始学习，目前只能想出这个办法求解