... a1,b1,c1:";cin>>a1>>b1>>c1;cout<<"Nhap lan luot cac he so a2,b1,c2:";cin>>a2>>b2>>c2;d=dt(a1,b1,a2,b2);dx=dt(c1,b1,c2,b2);dy=dt(a1,c1,a2,c2);if(d!=0){cout<<"HPT bac 1 hai ... tính 2 ẩn.#include "stdafx.h"#include <iostream>using namespace std;double dt(double a1, double b1, double a2, double b2){return a1*b2-a2*b1;}void main(){double a1,b1,c1,a2,b2,c2,d,dx,dy;cout<<"Nhap ... cout<<"PTB2 vo nghiem !"<<endl;else if (d==0) cout<<"PTB2 co nghiem kep X="<<-b /2/ a<<endl;else{x1=(-b+sqrt(d)) /2/ a;x2=(-b-sqrt(d)) /2/ a;cout<<"PTB2 co 2...