题解 | #计算一元二次方程#

#include <stdio.h>
#include <math.h>
int main()
{
	double a, b,c;
	while (scanf("%lf %lf %lf", &a, &b, &c) != EOF)
	{
		if(a==0){
			printf("Not quadratic equation\n");
		}
		else{
            double d = b * b - 4 * a * c;
            //虚数根
			if (d<0){
                d=sqrt(-d) / (2 * a);
                if(d<0)d=-d;//虚部为负取反
				printf("x1=%.2lf-%.2lfi;x2=%.2lf+%.2lfi\n", (-b)/(2*a),d,(-b)/(2*a),d);
            } else if(d>0){//两个相等实根
                printf("x1=%.2lf;x2=%.2lf\n",(-b-sqrt(d))/(2*a),(-b+sqrt(d))/(2*a));
            }else{//两个不相等实根
				if ((-b)/(2*a)==-0.00){
                    printf("x1=x2=0.00\n");
                   }else{
                    printf("x1=x2=%.2lf\n", -b/(2*a));
                }
			}				
        }
			
	}
	return 0;
}