c13-1.cpp

这我们老师对是面向对象程序设计（清华大学出版社）一书制作的PPT

#include <iostream>
#include <math.h>
using namespace std;
int main()
{float a,b,c,disc;
 cout<<"please input a,b,c:";
 cin>>a>>b>>c;
 if (a==0)
  cerr<<"a is equal to zero,error!"<<endl;
 else
  if ((disc=b*b-4*a*c)<0)
   cerr<<"disc=b*b-4*a*c<0"<<endl;
  else
   {cout<<"x1="<<(-b+sqrt(disc))/(2*a)<<endl;
    cout<<"x2="<<(-b-sqrt(disc))/(2*a)<<endl;
   }
 return 0;
}