2.1.2 用逻辑代数定律证明下列等式:-|||-(1) +overline (A)B=A+B-|||-__-|||-(2) +Aoverline (B)C+ABoverline (C)=AB+AC-|||-(3) +Aoverline (B)overline (C)+overline (A)CD+(overline (C)+overline (D))E=A+CD+E-|||-(4) (A+B)(A+overline (B))=A-|||-(5) +overline (A)C+BCD=AB+overline (A)C-|||-(6) (A+B)(B+C)(A+C)=(A+B)(A+C)