第一题

#include <iostream>
#include <cmath>
using namespace std;
double q(double,double,double);
int main()
{double a,b,c,p,x1,x2;
cout<<"please enter a,b,c:";
cin>>a>>b>>c;
p=-b/(2*a);
try
{x1=p+q(a,b,c);
x2=p-q(a,b,c);
cout<<"x1="<<x1<<endl<<"x2="<<x2<<endl;
}
catch(double d)
{cout<<"a="<<a<<",b="<<b<<",c="<<c<<",disc="<<d<<",error!"<<endl;}
cout<<"end"<<endl;
}

double q(double a,double b,double c)
{double disc;
disc=b*b-4*a*c;
if (disc<0) throw disc;
return sqrt(disc)/(2*a);
}

<img src="https://img-blog.csdn.net/20150624230040354?watermark/2/text/aHR0cDovL2Jsb2cuY3Nkbi5uZXQvbW9sdXpodWk=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70/gravity/Center" alt="" />