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3 and 4 .Determinants and Matrices
easy
$\left| {\,\begin{array}{*{20}{c}}{{b^2} - ab}&{b - c}&{bc - ac}\\{ab - {a^2}}&{a - b}&{{b^2} - ab}\\{bc - ac}&{c - a}&{ab - {a^2}}\end{array}\,} \right| = $
A
$abc(a + b + c)$
B
$3{a^2}{b^2}{c^2}$
C
$0$
D
None of these
Solution
(c) $\Delta = (b – a)\,(b – a)\,.\,\left| {\,\begin{array}{*{20}{c}}b&{b – c}&c\\a&{a – b}&b\\c&{c – a}&a\end{array}\,} \right|$
= ${(a – b)^2}\left| {\,\begin{array}{*{20}{c}}b&b&c\\a&a&b\\c&c&a\end{array}\,} \right|\, = 0$, [by ${C_2} \to {C_2} + {C_3}$] .
Standard 12
Mathematics