Keo theo: ->

a->b = -b -> -a = -a v b = -(a ^ -b)

Hoi : ^

a ^b = -(a-> -b) = -(b -> -a) = -(-a v -b)

Tuyen : v

a v b= -a -> b = -b -> a = -(-a ^ -b)

Phu dinh: -

-(a->b) = a ^ -b

-(a v b) = -a ^ -b

-(a^b) = -a v -b