题解 | #计算一元二次方程#

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

int main()
{
    double a = 0.0;
    double b = 0.0;
    double c = 0.0;
    double x1 = 0.0;
    double x2 = 0.0;
    while (scanf("%lf %lf %lf", &a, &b, &c) != EOF)
    {
        if (0 == a)//判断a是否为0
        {
            printf("Not quadratic equation\n");
        }
        else
        {
            c = b * b - 4 * a * c;//由于后面的计算用不上原来的c了，所以给c赋上新的值△
            if (0 == c)//有两个相等的实数根
            {
                x1 = -b / (2 * a) + 0;
                printf("x1=x2=%.2lf\n", x1);
            }
            else if (c > 0)//有两个不相等的实数根
            {
                x1 = (-b - sqrt(c)) / (2 * a);
                x2 = (-b + sqrt(c)) / (2 * a);
                printf("x1=%.2lf;x2=%.2lf\n", x1, x2);
            }
            else//解为复数
            {
                x1 = (-b) / (2 * a);
                x2 = sqrt(-c) / (2 * a);
                printf("x1=%.2lf-%.2lfi;x2=%.2lf+%.2lfi\n", x1, x2, x1, x2);
            }
        }
    }
    return 0;
}