discrete math

hi can some body guide me for getting the logical equivalence of this problem
¬(a→b) ↔ a^¬b = a→(b→a)

 

¬(a→b)= a^¬b

a^¬b ↔a^¬b


i dont know whats next.

 

"a→(b→a)" is a tautology since if a is true then anything implies a: both T→T and F→T are true.

It is "=" to "¬(a→b) ↔ a^¬b" since that is also a tautology. If a→b is not true then a is true but b is false and so a^¬b is also true.