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Qualcomm Digital Electronics Digital Electronics Medium

QUESTION 21 Simplify the boolean equation given below?

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QUESTION 21

Simplify the boolean equation given below?

Y = (A + B)' + A'B + A

Choose one option.
Show answer & explanation
Answer: C. Y = 1

When A = 1, the term A dominates and makes Y = 1. When A = 0, the term (A + B)' = (0 + B)' = B', and A'B = 1·B = B, so Y = B' + B + 0 = 1 (by the law of complementarity). Therefore, Y is always 1 regardless of input values.

Step-by-step Derivation:
Step 1: Apply De Morgan's Law to (A + B)': (A + B)' = A'B'

Step 2: Rewrite the equation:
Y = A'B' + A'B + A

Step 3: Factor out A' from the first two terms:
Y = A'(B' + B) + A

Step 4: Apply the complement law (B' + B = 1):
Y = A'(1) + A
Y = A' + A

Step 5: Apply the law of complementarity (A' + A = 1):
Y = 1

Verification by truth table:

A B (A+B)' A'B A Y
0 0 1 0 0 1
0 1 0 1 0 1
1 0 0 0 1 1
1 1 0 0 1 1

All outputs are 1, confirming Y = 1.