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The matrix P is the inverse of a matrix Q. If I denotes the identity matrix, which one of the following options is correct ?
  • a)
    PQ = I but QP ≠ I 
  • b)
    QP = I but PQ ≠ I
  • c)
    PQ = I and QP = I 
  • d)
    PQ − QP = I
Correct answer is option 'C'. Can you explain this answer?
Verified Answer
The matrix P is the inverse of a matrix Q. If I denotes the identity m...
Given P is inverse of Q 
⇒ PQ = QP = I
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Most Upvoted Answer
The matrix P is the inverse of a matrix Q. If I denotes the identity m...
Explanation:

To understand why option 'C' is the correct answer, let's first review the properties of matrix inverses.

Matrix Inverse:
The inverse of a square matrix Q, denoted as Q^(-1), is a matrix such that when it is multiplied by the original matrix Q, the result is the identity matrix I. In other words, Q^(-1) * Q = I.

Now, let's consider the given information that matrix P is the inverse of matrix Q.

Option Analysis:

a) PQ = I but QP ≠ I
This option suggests that PQ equals the identity matrix I, but QP is not equal to the identity matrix. However, this contradicts the definition of matrix inverses, as Q^(-1) * Q should equal I. Therefore, this option is incorrect.

b) QP = I but PQ ≠ I
This option suggests that QP equals the identity matrix I, but PQ is not equal to the identity matrix. Again, this contradicts the definition of matrix inverses, as Q^(-1) * Q should equal I. Therefore, this option is also incorrect.

c) PQ = I and QP = I
This option suggests that both PQ and QP are equal to the identity matrix I. This aligns with the definition of matrix inverses, as Q^(-1) * Q equals I. Therefore, this option is correct.

d) PQ * QP = I
This option suggests that the product of PQ and QP is equal to the identity matrix I. While matrix multiplication is associative, meaning (AB)C = A(BC), it is not necessarily commutative, meaning AB ≠ BA in general. Therefore, this option is incorrect.

Conclusion:
Based on the properties of matrix inverses, the correct answer is option 'c) PQ = I and QP = I'. This aligns with the definition of matrix inverses and ensures that both PQ and QP result in the identity matrix I.
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The matrix P is the inverse of a matrix Q. If I denotes the identity matrix, which one of the following options is correct ?a)PQ = I but QP ≠ Ib)QP = I but PQ ≠ Ic)PQ = I and QP = Id)PQ − QP = ICorrect answer is option 'C'. Can you explain this answer?
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