Gujarati
3 and 4 .Determinants and Matrices
medium

$x$ के कितने मानों के लिये आव्यूह $\left[ {\begin{array}{*{20}{c}}3&{ - 1 + x}&2\\3&{ - 1}&{x + 2}\\{x + 3}&{ - 1}&2\end{array}} \right]$ अंतराल $[ - 4,\,\, - 1]$ में अव्युत्क्रमणीय होगा

A

$2$

B

$0$

C

$3$

D

$1$

Solution

(d) आव्यूह के अव्युत्क्रमणीय होने के लिए, $\left| {\,\begin{array}{*{20}{c}}3&{ – 1 + x}&2\\3&{ – 1}&{x + 2}\\{x + 3}&{ – 1}&2\end{array}\,} \right|\, = 0$
==> $\left| {\,\begin{array}{*{20}{c}}3&{ – 1 + x}&2\\0&{ – x}&x\\x&{ – x}&0\end{array}\,} \right|\, = 0$, $\,[{R_2} \to {R_2} – {R_1},\,{R_3} \to {R_3} – {R_1}]$
==> $\left| {\,\begin{array}{*{20}{c}}{x + 4}&{ – 1 + x}&2\\0&{ – x}&x\\0&{ – x}&0\end{array}\,} \right|\, = 0$, $[{C_1} \to {C_1} + {C_2} + {C_3}]$
==> $(x + 4)\,(0 + {x^2}) = 0 \Rightarrow x = – 4,\,0$.
ध्यान दें $ – 4 \in [ – 4,\, – 1]$.

Standard 12
Mathematics

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