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3 and 4 .Determinants and Matrices
easy
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
$a \ne 1$
B
$a = 1$
C
$a = 0$
D
$a = - 1$
Solution
(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 $a = 1.$
Standard 12
Mathematics