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STD 12 - 3 and 4 . determinant and metrices — Mathematics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceMathematicsSTD 12 - 3 and 4 . determinant and metrices1 Mark
MCQ
If matrix $A = \left[ {\begin{array}{*{20}{c}}3&2&4\\1&2&{ - 1}\\0&1&1\end{array}} \right]$and ${A^{ - 1}} = \frac{1}{K}adj(A),$ then $K$is
  • A
    $7$
  • B
    $-7$
  • C
    $\frac{1}{7}$
  • ✓
    $11$
✓

Answer

Correct option: D.
$11$
d
(d)$K = \,|A|$; $|A|\,\, = \left| {\,\begin{array}{*{20}{c}}3&2&4\\1&2&{ - 1}\\0&1&1\end{array}\,} \right|\, = \,\,11$.

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