3-2.cpp

来自「为初学者提供的最佳的C++程序设计源程序库」· C++ 代码 · 共 19 行

#include<iostream.h>
#include<math.h>
void main()
{
  float a,b,c,d;
  cout<<"a=";cin>>a;
  cout<<"b=";cin>>b;
  cout<<"c=";cin>>c;
  d=b*b-4*a*c;
  if(a==0)
    cout<<"不是二次方程！"<<endl;
  else if(d==0)
    cout<<"一个实根:"<<-b/(2*a)<<endl;
  else if(d>0)
    cout<<"两个实根:"<<(-b+sqrt(d))/(2*a)<<","
        <<(-b-sqrt(d))/(2*a)<<endl;
  else
    cout<<"无实根!"<<endl;
}