Question

Which of the following is not a valid rule of Boolean Algebra?
1. A + A' = A
2. A ⋅ A = A
3. A ⋅ A' = 0
4. A + A' = 1

Answer 1

Correct Answer - Option 1 : A + A' = A

Option 1: It is not valid

A + A' = 1   by Inverse Law

Boolean algebra laws

Name	AND Form	OR Form
Identity law	1.A = A	0 + A = A
Null Law	0.A = 0	1 + A = 1
Idempotent Law	A. A = A	A + A = A
Inverse Law	AA’ = 0	A + A’ = 1
Commutative Law	AB = BA	A + B = B + A
Associative Law	(AB)C	(A + B) + C = A + (B + C)
Distributive Law	A + BC = (A + B) (A + C)	A (B + C) = AB + AC
Absorption Law	A (A + B) = A	A + AB = A
De Morgan’s Law	(AB)’ = A’ + B’	(A + B)’ = A’B’