MCQ
If $P = \left[ {\begin{array}{*{20}{c}}1&2&3\\2&3&4\\3&4&5\end{array}} \right]\,\left[ {\begin{array}{*{20}{c}}{ - 1}&{ - 2}\\{ - 2}&0\\0&{ - 4}\end{array}} \right]$$\left[ {\begin{array}{*{20}{c}}{ - 4}&{ - 5}&{ - 6}\\0&0&1\end{array}} \right]$ then ${P_{22}} = $
  • $40$
  • B
    $-40$
  • C
    $-20$
  • D
    $20$

Answer

Correct option: A.
$40$
a
(a) $P = {\left[ {\begin{array}{*{20}{c}}1&2&3\\2&3&4\\3&4&5\end{array}} \right]_{3 \times 3}}{\left[ {\begin{array}{*{20}{c}}{ - 1}&{ - 2}\\{ - 2}&0\\0&{ - 4}\end{array}} \right]_{3 \times 2}}{\left[ {\begin{array}{*{20}{c}}{ - 4}&{ - 5}&{ - 6}\\0&0&1\end{array}} \right]_{2 \times 3}}$
$P = {\left[ {\begin{array}{*{20}{c}}{ - 3}&{ - 14}\\{ - 8}&{ - 20}\\{ - 11}&{ - 26}\end{array}} \right]_{3 \times 2}}{\left[ {\begin{array}{*{20}{c}}{ - 4}&{ - 5}&{ - 6}\\0&0&1\end{array}} \right]_{2 \times 3}}$
$P = {\left[ {\begin{array}{*{20}{c}}{12}&{15}&4\\{32}&{40}&{28}\\{44}&{55}&{40}\end{array}} \right]_{3 \times 3}}$$ \Rightarrow $ ${P_{22}} = 40$.

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