I'm fairly new to Boolean algebra and I was wondering, using Boolean theorems,can any Boolean expression with an OR operators in it be converted to an equivalent expression using only AND operators? Do some expressions come to a point where you don't have any choice but to use OR operators?
For example, I have tried to simplify the following expression into only AND operators, but I don't think I'm getting the write answer:
xy'z' + x'y'z = y'(xz' + x'z) = y'(xz' + (xz')') = y'(1) = y'
y' isn't the right answer as it has different truth tables to the original expression. So what am I doing wrong in my simplification? And can you convert any expression with an OR to one with only AND's?