доброе время суток,подскажите что не так?программа в С++

#include<iostream.h>
#include<conio.h>
#include<math.h>
int main ()
{
int xn,xk,a,b,c,dx;
float f;
clrscr();
cout<<endl<<"vveite a=";
cin>>a;
cout<<endl<<"vvedite b=";
cin>>b;
cout<<endl<<"vveite c=";
cin>>c;
cout<<endl<<"vvedite xn=";
cin>>xn;
cout<<endl<<"vvedite xk=";
cin>>xk;
cout<<endl<<"vvedite dx=";
cin>>dx;
cout<<" x= | y= "<<endl;
cout<<"----|----"<<endl;
do
{
if(c<0 && xn!=0) f=-a*xn-c;
if(c>0 && xn==0) f= xn-a/-c;
if(c==0) f=b*xn/c-a;
cout<<" "<<xn;
cout<<"    "<<f<<endl;
xn=xn+dx;
}
while(xn!=xk);
getch();
return 0;
}

using namespace std;

std::cout       std::cin

#include <iostream>
#include <conio.h>
#include <cmath>
 
using std::cout;       
using std::cin;
using std::endl;
 
int main ()
{
double xn,xk,a,b,c,dx,f;
 
cout << "Enter a:";
cin >> a;
cout << "Enter b:";
cin >> b;
cout << "Enter c:";
cin >> c;
cout << "Enter xn:";
cin >> xn;
cout << "Enter xk:";
cin >> xk;
cout << "Enter dx:";
cin >> dx;
cout << " x= | y= "<<endl;
cout << "----|----"<<endl;
 
do
{
if(c<0 && xn != 0) 
    f=-a*(xn-c);
 
if(c>0 && xn == 0) 
    f= (xn-a)/-c;
 
if(c == 0) 
    f=(b*xn)/(c-a);
cout << " "  << xn;
cout<<"    "<<f<<endl;
xn=xn+dx;
}
while(xn != xk);
_getch();
return 0;
}