C++ Help

[FolloweR]

Hmm, I thought it would work with that, but I guess I've done something wrong again.. I tried substituting y=x*x, but it said x isn't initialized.

That's the code:

Code:

#include <iostream>
#include <cmath>
using namespace std;
int main()
{
        double a,b,c,y1,y2,D;
        cout<<"Enter a,b,c:"<<endl;
        cin>>a>>b>>c;
        if(a==0&&b==0&&c==0) cout<<"Every x is solution"<<endl;
        if(a==0&&b!=0)cout<<"y="<<-c/b<<"x1="<<sqrt(-c/b)<<"x2="<<-sqrt(-c/b)<<endl;
    if(a!=0) {
        D=b*b-4*a*c;
        y1=(-b-sqrt(D))/(2*a);
        y2=(-b+sqrt(D))/(2*a);
    if(D>0) {
        cout<<"y1="<<y1<<"x1="<<sqrt(y1)<<"x2="<<-sqrt(y1)<<endl;
        cout<<"y2="<<y2<<"x3="<<sqrt(y2)<<"x4="<<-sqrt(y2)<<endl;}
    if(D==0)cout<<"y1=y2="<<-b/(2*a)<<"x1="<<sqrt(-b/(2*a))<<"x2="<<-sqrt(-b/(2*a))<<endl;
    if(D<0)cout<<"No real roots"<<endl;
    }
    return 0;
    }