Which of the following expressions is not equivalent to NOT X, denoted X′?
1999
Which of the following expressions is not equivalent to NOT X, denoted X′?
- A.
X NAND X
- B.
X NOR X
- C.
X NAND 1
- D.
X NOR 1
Attempted by 126 students.
Show answer & explanation
Correct answer: D
The correct answer is: X NOR 1.
Here, NOT X is denoted by X′. Evaluate each expression:
X NAND X = NOT(X AND X) = NOT X = X′.
X NOR X = NOT(X OR X) = NOT X = X′.
X NAND 1 = NOT(X AND 1) = NOT X = X′.
X NOR 1 = NOT(X OR 1) = NOT(1) = 0.
Since X NOR 1 is always 0 and is not equal to NOT X for all input values, it is the expression that is not equivalent to X′.