Question

A student makes a mistake somewhere in the process of simplifying the following Boolean expression:

(x'y+z)'
= (x'y)'.z'
= (x')'+y'.z'
= x+y'.z

Determine what the mistake is?

Answer 1

The mistake is in the last step. The term z' must multiply both terms inside the bracket.

Correct steps:

(x′y + z)′​ = (x′y)′z′
             = (x + y′)z′
             = xz′ + y′z′​

Simplified expression:

xz′ + y′z′