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STD 12 - 3 and 4 . determinant and metrices — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEESTD 12 - 3 and 4 . determinant and metrices4 Marks
MCQ
The value of a for which the matrix $A = \left( {\begin{array}{*{20}{c}}a&2\\2&4\end{array}} \right)$is singular if
  • A
    $a \ne 1$
  • ✓
    $a = 1$
  • C
    $a = 0$
  • D
    $a = - 1$
✓

Answer

Correct option: B.
$a = 1$
b
(b) Put $a = 1$; $\therefore $ $|A| = \left| {\,\begin{array}{*{20}{c}}1&2\\2&4\end{array}\,} \right| = 4 - 4 = 0$
Hence, $A$ is a singular matrix for $a = 1.$

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