Which is the simplest boolean expression of ab + (a + b)' + (a'b)'?

Question

I have this Boolean expression:

$y = ab + (a + b)' + (a'b)'$

$ = ab + a'b' + a + b'$

$ = a(1 + b) + b'(1 + a')$

$ = a + b'$

Is $(a + b')$ the simplest answer or:

$a + b' = (a'b)'$ the simplest?

Thank you for help.

Answer 1

Generally, an expression is only considered "simplified" if each "not" (that is, each ') is applied directly to a variable. I would say that $(a'b)'$ is not simplified because the outer ' is applied to $(a'b)$ as opposed to $a$ or $b$.

So, $a + b'$ is certainly a simpler form than $(a'b)'$.