2 , , | , * 20 c 1&1&1 &b&c a^2 - bc & b^2 - ac & c^2 - ab , | = - Vidyadip

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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