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AP EAMCET · Maths · Matrices

If \(\left[\begin{array}{ccc}5 & a & -7 \\ b & -7 & c \\ -7 & d & -1\end{array}\right]\) is the adjoint of the matrix \(\left[\begin{array}{lll}1 & 2 & 3 \\ 2 & 3 & 1 \\ 3 & 1 & 2\end{array}\right]\), then \(a+b+c+d=\)

  1. A \(8\)
  2. B \(10\)
  3. C \(0\)
  4. D \(2\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(8\)

Step-by-step Solution

Detailed explanation

\begin{aligned} & C_{11}=(-1)^{1+1}(3 \times 2-1 \times 1)=5 \\ & C_{12}=(-1)^{1+2}(2 \times 2-3 \times 1)=-1 \\ & C_{13}=(-1)^{1+3}(2 \times 1-3 \times 3)=-7 \\ & C_{21}=(-1)^{2+1}(4-3)=-1 \\ & C_{22}=(-1)^{2+2}(2-9)=-7 \\ & C_{23}=(-1)^{2+3}(1-6)=5 \\ &…

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