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The Boolean expression \((\overline{AB})(\bar{A} + B)(A + \bar{B})\) can be simplified to

  • A.\(A + B\)
  • B.\(\bar{A}B\)
  • C.\(\overline{A + B}\)
  • D.\(AB\)

Answer: C

The expression simplifies to \(\overline{A + B}\).

First multiply the last two factors:

\[ \begin{aligned} (\bar{A} + B)(A + \bar{B}) &= \bar{A}\bar{B} + AB \\ \overline{AB}\,(\bar{A}\bar{B} + AB) &= (\bar{A} + \bar{B})\bar{A}\bar{B} + 0 \\ &= \bar{A}\bar{B} = \overline{A + B} \end{aligned} \]

The product \(\overline{AB}\cdot AB\) is zero, leaving only \(\bar{A}\bar{B}\), which by De Morgan's law is the NOR \(\overline{A + B}\). Checking with \(A = B = 1\): the expression is 0, which rules out \(A + B\) and \(AB\); with \(A = 0, B = 1\) it is 0, which rules out \(\bar{A}B\).

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