Answer
a. The entire circuit is equivalent to a single OR gate.
b. This entire circuit is also equivalent to a single XOR gate.
Work Step by Step
a). If the output of an AND gate is passed through a NOT gate, the combination
computes the Boolean operation called NAND, which has an output of 0 only when both its inputs are 1.
The symbol for a NAND gate is the same as an AND gate except that it has a circle at its output.
The figure $a$ is a circuit containing a NAND gate.
-The entire circuit is equivalent to a single OR gate.
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b) If the output of an OR gate is passed through a NOT gate,
the combination computes the Boolean operation called NOR that has an output
of 1 only when both its inputs are 0.
The symbol for a NOR gate is the same as an OR gate except that it has a circle at its output. The following
is a circuit containing an AND gate and two NOR gates.
