Question

Prove (giving reasons) that [(x + y)’ + (x + y)’]’ = x + y

Answer 1

Explanation:

[(x + y)’ + (x + y)’]’ = ((x + y)’)’.((x + y)’)’ (Using De Morgan’s first theorem i.e., (A + B)’ = A’.B’) = (x + y).(x + y) (∵X’ = X) = x + y