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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
$2\,\,\left| {\,\begin{array}{*{20}{c}}1&1&1\\a&b&c\\{{a^2} - bc}&{{b^2} - ac}&{{c^2} - ab}\end{array}\,} \right| = $
  • ✓
    $0$
  • B
    $1$
  • C
    $2$
  • D
    $3abc$
✓

Answer

Correct option: A.
$0$
a
(a) We have $2\,\,\left| {\,\begin{array}{*{20}{c}}1&1&1\\a&b&c\\{{a^2} - bc}&{{b^2} - ac}&{{c^2} - ab}\end{array}\,} \right|$

= $2\,\left| {\,\begin{array}{*{20}{c}}1&1&1\\a&b&c\\{{a^2}}&{{b^2}}&{{c^2}}\end{array}\,} \right| - 2\left| {\,\begin{array}{*{20}{c}}1&1&1\\a&b&c\\{bc}&{ac}&{ab}\end{array}\,} \right|$

= $2\,\left| {\,\begin{array}{*{20}{c}}1&1&1\\a&b&c\\{{a^2}}&{{b^2}}&{{c^2}}\end{array}\,} \right| - \frac{2}{{abc}}\left| {\,\begin{array}{*{20}{c}}a&b&c\\{{a^2}}&{{b^2}}&{{c^2}}\\{abc}&{abc}&{abc}\end{array}\,} \right|$

                                                                     { Applying ${C_1}(a),{C_2}(b),{C_3}(c)$}

$ = 2\,\left| {\,\begin{array}{*{20}{c}}1&1&1\\a&b&c\\{{a^2}}&{{b^2}}&{{c^2}}\end{array}\,} \right| - \frac{2}{{abc}}(abc)\,\left| {\,\begin{array}{*{20}{c}}a&b&c\\{{a^2}}&{{b^2}}&{{c^2}}\\1&1&1\end{array}\,} \right| = 0$.

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