MCQ
If $A = \left[ {\begin{array}{*{20}{c}}1&0\\2&0\end{array}} \right],B = \left[ {\begin{array}{*{20}{c}}0&0\\1&{12}\end{array}} \right]$, then
  • A
    $AB = O,BA = O$
  • $AB = O,BA \ne O$
  • C
    $AB \ne O,BA = O$
  • D
    $AB \ne O,BA \ne O$

Answer

Correct option: B.
$AB = O,BA \ne O$
b
(b) $AB = \,\left[ {\begin{array}{*{20}{c}}1&0\\2&0\end{array}\,} \right]\,\left[ {\begin{array}{*{20}{c}}0&0\\1&{12}\end{array}} \right] = \left[ {\begin{array}{*{20}{c}}0&0\\0&0\end{array}} \right] = O$

while $BA = \left[ {\begin{array}{*{20}{c}}0&0\\1&{12}\end{array}} \right]\,\left[ {\begin{array}{*{20}{c}}1&0\\2&0\end{array}} \right] = \left[ {\begin{array}{*{20}{c}}0&0\\{25}&0\end{array}} \right]\, \ne O$.

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