程序代码：

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

int main(void)
{
    
    double a, b, c;
    double delta;
    double x1, x2;
    char ch;
    
    printf("输入方程的系数:\n");

    printf("a = ");
    scanf("%lf", &a);
    
    printf("b = ");
    scanf("%lf", &b);
    
    printf("c = ");
    scanf("%lf", &c);
    
    
    delta =b*b-4*a*c;
    
    if (delta > 0)
    {
        x1 = (-b+sqrt(delta))/(2*a);
        x2 = (-b-sqrt(delta))/(2*a);
        printf("有两个答案, x1 = %lf , x2 = %lf\n", x1, x2);
    }
    else if (delta == 0);//这里多了一个分号
    {
        x1 = x2 = (-b)/(2*a);
        printf("唯一答案, x1 = x2 %lf\n", x1 ,x2);
    }
    else
    {
        printf("无答案\n");
    }
    
    return 0;
}

[此贴子已经被作者于2016-4-22 17:56编辑过]

程序代码：

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

int main(void)
{
    
    double a, b, c;
    double delta;
    double x1, x2;
    char ch;
    do
    {
        printf("输入方程的系数:\n");
        
        printf("a = ");
        scanf("%lf", &a);
        
        printf("b = ");
        scanf("%lf", &b);
        
        printf("c = ");
        scanf("%lf", &c);
        
        
        delta =b*b-4*a*c;
        
        if (delta > 0)
        {
            x1 = (-b+sqrt(delta))/(2*a);
            x2 = (-b-sqrt(delta))/(2*a);
            printf("有两个答案, x1 = %lf , x2 = %lf\n", x1, x2);
        }
        else if (delta == 0)
        {
            x1 = x2 = (-b)/(2*a);
            printf("唯一答案, x1 = x2 %lf\n", x1 ,x2);
        }
        else
        {
            printf("无答案\n");
        }
        
        printf("想继续吗(y/n):");
        scanf(" %c", &ch);
    }
    while ('y' == ch || 'Y' == ch);
    return 0;
}

[此贴子已经被作者于2016-4-22 17:55编辑过]