Question

In Boolean algebra, $\overline{ \bar{A} . \bar{B}}$ is equal to

• A. $\bar{A} . \bar{B}$
• B. $\bar{A} + \bar{B}$
• C. $A.B$
• D. $A + B$

Answer 1

Answer: (D)

According to De-Morgan's theorem
$\bar{A} \cdot \bar{B}=(\overline{A+B})$
$\therefore (\overline{\bar{A} \cdot \bar{B}})=(\overline{\bar{A}+\bar{B}})$
$=(A+B) (\because \overline{\bar{A}}=A) $
$ \therefore (\overline{\bar{A} \cdot \bar{B}}) =(A+B) $