Which one of the following is NOT a valid identity?

This question was previously asked in
GATE CS 2019 Official Paper
View all GATE CS Papers >
  1. (x ⊕ y) ⊕ z = x ⊕ (y ⊕ z)
  2. (x + y) ⊕ z = x ⊕ (y + z)
  3. x ⊕ y = x + y, if xy = 0
  4. x ⊕ y = (xy + x'y')'

Answer (Detailed Solution Below)

Option 2 : (x + y) ⊕ z = x ⊕ (y + z)
Free
GATE CS Full Mock Test
65 Qs. 100 Marks 180 Mins

Detailed Solution

Download Solution PDF

1. (x ⊕ y) ⊕ z = x ⊕ (y ⊕ z) 

x

y

z

(x ⊕ y) ⊕ z

x ⊕ (y ⊕ z)

0

0

0

0

0

0

O

1

1

1

0

1

0

0

1

0

1

1

0

0

1

0

0

1

1

1

0

1

0

0

1

1

0

0

0

1

1

1

1

1

 

Therefore exclusive OR is associative and hence (x ⊕ y) ⊕ z = x ⊕ (y ⊕ z) 

2.

x

y

z

(x + y) ⊕ z

x ⊕ (y + z)

0

0

0

0

0

0

O

1

1

1

0

1

0

0

1

0

1

1

0

1

1

0

0

1

1

1

0

1

0

0

1

1

0

1

0

1

1

1

0

0

 

(x + y) ⊕ z ≠ x ⊕ (y + z) ∴ is it not a valid identity

3.

xy = 0

Checking validity

X

y

x + y

x ⊕ y

0

0

0

0

0

1

1

1

1

0

1

1

x + y = x ⊕ y / if xy = 0

4.

(xy + x'y')'

= (x’ + y’).(x+y) / Demorgan’s Law

= x’y +xy’

= x ⊕ y

Latest GATE CS Updates

Last updated on Jan 8, 2025

-> GATE CS 2025 Admit Card has been released on 7th January 2025.

-> The exam will be conducted on 1st February 2025 in 2 shifts.

-> Candidates applying for the GATE CE must satisfy the GATE Eligibility Criteria.

-> The candidates should have BTech (Computer Science). Candidates preparing for the exam can refer to the GATE CS Important Questions to improve their preparation.

-> Candidates must check their performance with the help of the GATE CS mock tests and GATE CS previous year papers for the GATE 2025 Exam.

Hot Links: teen patti master gold download teen patti all game teen patti online all teen patti