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3 and 4 . determinant and metrices — Maths STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceMaths3 and 4 . determinant and metrices1 Mark
MCQ
The value of the determinant $\left| {\,\begin{array}{*{20}{c}}a&{a\, + \,b}&{a\, + \,2b}\\{a\, + \,2b}&a&{a\, + \,b}\\{a\, + \,b}&{a\, + \,2b}&a\end{array}\,} \right|$ is
  • A
    $9a^2 (a + b)$
  • ✓
    $9b^2 (a + b)$
  • C
    $3b^2 (a + b)$
  • D
    $7a^2 (a + b)$
✓

Answer

Correct option: B.
$9b^2 (a + b)$
b
Use $R_2 \rightarrow R_2 -R_1$ and $R_3 \rightarrow R_3 -R_1$ and expand

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