MCQ
If ${\Delta _1} = \left| {\,\begin{array}{*{20}{c}}1&0\\a&b\end{array}\,} \right|$ and ${\Delta _2} = \left| {\begin{array}{*{20}{c}}1&0\\c&d\end{array}} \right|$, then ${\Delta _2}{\Delta _1}$is equal to
  • A
    $ac$
  • $bd$
  • C
    $(b - a)(d - c)$
  • D
    None of these

Answer

Correct option: B.
$bd$
b
(b) ${\Delta _2}{\Delta _1} = \left| {\begin{array}{*{20}{c}}1&0\\c&d\end{array}} \right|\,\,\left| {\,\begin{array}{*{20}{c}}1&0\\a&b\end{array}\,} \right| = \left| {\,\begin{array}{*{20}{c}}1&0\\{c + ad}&{bd}\end{array}\,} \right| = bd$.

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