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NDA 2025
Exam
NDA
Year
2025
Subject
Mathematics
Chapter
Matrices

NDA 2025 · Mathematics · Matrices

What is the value of the determinant of the inverse of the matrix...

What is the value of the determinant of the inverse of the matrix \begin{pmatrix} -4 & -5 \\ 2 & 2 \end{pmatrix}?

Options

  1. A12\dfrac{1}{2}
  2. B11
  3. C22
  4. D44

Correct answer

A. 12\dfrac{1}{2}

Step-by-step solution

Let A=(−4−522)A = \begin{pmatrix} -4 & -5 \\ 2 & 2 \end{pmatrix}.

The determinant of matrix AA is given by:

∣A∣=(−4)(2)−(−5)(2)|A| = (-4)(2) - (-5)(2)

∣A∣=−8+10=2|A| = -8 + 10 = 2

The determinant of the inverse of a matrix is the reciprocal of the determinant of the matrix, i.e., ∣A−1∣=1∣A∣|A^{-1}| = \dfrac{1}{|A|}.

∣A−1∣=12|A^{-1}| = \dfrac{1}{2}

Answer: 12\dfrac{1}{2}
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