658.一元二次方程公式
#include<stdio.h>
#include<math.h>
int main()
{
double a,b,c,R1,R2;
scanf("%lf %lf %lf",&a,&b,&c);
if(b*b-4*a*c<0||a==0){
printf("Impossivel calcular");
return 0;}
else
R1=(-b+sqrt(b*b-4*a*c))/(2*a);
R2=(-b-sqrt(b*b-4*a*c))/(2*a);
printf("R1 = %.5f\nR2 = %.5f\n",R1,R2);
return 0;
}