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3 and 4 .Determinants and Matrices
medium
If the system of equations, $x + 2y - 3z = 1$, $(k + 3)z = 3,$ $(2k + 1)x + z = 0$is inconsistent, then the value of $ k$ is
A
$-3$
B
$1/2$
C
$0$
D
$2$
Solution
(a) For the equation to be inconsistent $D = 0$
$\therefore $$D = \left| {\,\begin{array}{*{20}{c}}1&2&{ – 3}\\0&0&{k + 3}\\{2k + 1}&0&1\end{array}\,} \right| = 0 \Rightarrow k = – 3$
and ${D_1} = \left| {\,\begin{array}{*{20}{c}}1&2&{ – 3}\\3&0&0\\0&0&1\end{array}\,} \right| \ne 0$
So that system is inconsistent for $k = – 3$.
Standard 12
Mathematics