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CUET · MATHS · PYQ PAPER 2023

Sum of the minor and the cofactor of the element 6 in the determinant \(\left|\begin{array}{lll}2 & 3 & 1 \\ 4 & 5 & 6 \\ 7 & 8 & 9\end{array}\right|\) is :

  1. A -5
  2. B -10
  3. C 10
  4. D 0
Verified Solution

Answer & Solution

Correct Answer

(D) 0

Step-by-step Solution

Detailed explanation

\(M_{23} = \left| \begin{array}{cc} 2 & 3 \\ 7 & 8 \end{array} \right| = (2 \times 8) - (3 \times 7) = 16 - 21 = -5\) \(C_{23} = (-1)^{2+3} M_{23} = (-1)^5 (-5) = -1(-5) = 5\) \(M_{23} + C_{23} = -5 + 5 = 0\)
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