---

Lỗi biên dịch:

Main.cc: In function ‘int main()’:
Main.cc:8:5: error: ‘cin’ was not declared in this scope
     cin >> a >> b >> x >> y;
     ^~~
Main.cc:8:5: note: suggested alternative: ‘sin’
     cin >> a >> b >> x >> y;
     ^~~
     sin
Main.cc:9:5: error: ‘cout’ was not declared in this scope
     cout << (a*x)+(b*y);
     ^~~~
Main.cc:9:5: note: suggested alternative: ‘cosl’
     cout << (a*x)+(b*y);
     ^~~~
     cosl