1 A B !(A*!B+!A*B) A*B+!(A+B)

2 A B (A+B)*(A+C)*(!B+!C) A*(!B+!C)

3 A B !(!(!(A*B)*!(!(A*A)*!(B*B))) A*!B+!A*B

4 A B !A*(B+A*B)=!A*B