题解 | #计算一元二次方程#

#include <stdio.h>
#include<math.h>
int main() {
    double a, b, c, derta;
    double x1;
    double x2;
    while ((scanf("%lf %lf %lf", &a, &b, &c)) != EOF) {
        if (a == 0)
            printf("Not quadratic equation\n");
        else {
            derta = b * b - 4 * a * c;
            x1 = (-b - sqrt(derta)) / (2* a);
            x2 = (-b + sqrt(derta)) / (2* a);
            if(x1==0.00&&x2==0.00)//这里很奇怪，要自己把x1、x2等于0.00的情况写出来，要不然输出的结果始终是-0.00
            printf("x1=x2=0.00\n");
            else if (derta == 0)
                printf("x1=x2=%.2lf\n", x1);
            else if (derta > 0)
                printf("x1=%.2lf;x2=%.2lf\n", x1, x2);
            else
                printf("x1=%.2lf-%.2lfi;x2=%.2lf+%.2lfi\n", -b / (2 * a),
                       sqrt(-derta) / (2 * a),
                       -b / (2 * a), sqrt(-derta) / (2 * a));
        }
    }
    return 0;
}