3 and 4 .Determinants and Matrices
easy

सारणिक   $\left| {\,\begin{array}{*{20}{c}}{31}&{37}&{92}\\{31}&{58}&{71}\\{31}&{105}&{24}\end{array}\,} \right|$ का मान है

A

$-2$

B

$0$

C

$81$

D

इनमें से कोई नहीं

Solution

(b) $\left| {\,\begin{array}{*{20}{c}}{31}&{37}&{92}\\{31}&{58}&{71}\\{31}&{105}&{24}\end{array}\,} \right|\, = \,\left| {\,\begin{array}{*{20}{c}}{31}&{37}&{92}\\0&{21}&{ – 21}\\0&{47}&{ – 47}\end{array}\,} \right|$;by $\begin{array}{l}{R_3} \to {R_3} – {R_2}\\{R_2} \to {R_2} – {R_1}\end{array}$

= $\left| {\,\begin{array}{*{20}{c}}{31}&{129}&{92}\\0&0&{ – 21}\\0&0&{ – 47}\end{array}\,} \right| = 0$;

(by ${C_2} \to {C_2} + {C_3})$.

Standard 12
Mathematics

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