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Mathematics
Problem
Find the adjoint of the matrix
A
=
[
−
1
−
2
−
2
2
1
−
2
2
−
2
1
]
A = \begin{bmatrix} -1 & -2 & -2 \\ 2 & 1 & -2 \\ 2 & -2 & 1 \end{bmatrix}
A
=
−
1
2
2
−
2
1
−
2
−
2
−
2
1
and hence show that
A
⋅
(
adj
A
)
=
∣
A
∣
I
3
A \cdot (\text{adj } A) = |A| I_3
A
⋅
(
adj
A
)
=
∣
A
∣
I
3
[CBSE-2015]
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