1. Demonstrate by means of truth tables the validity of the following identities. a) DeMorgan's theorem for two variables X'Y' = X' + Y' ' is the bars that are above the letters. Can someone explain this to me? I mean the truth table is just gonna look like this: X'Y' X' Y' I just need to know where and 0's and 1's go and why. Seems so easy, but I haven't been able to understand it.