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Lỗi biên dịch:

Main.cc: In function ‘int main()’:
Main.cc:8:5: error: ‘cout’ was not declared in this scope
     cout<<(A*X)+(B*Y);
     ^~~~
Main.cc:8:5: note: suggested alternative: ‘cosl’
     cout<<(A*X)+(B*Y);
     ^~~~
     cosl