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3 and 4 .Determinants and Matrices
easy
જો $A = \left[ {\begin{array}{*{20}{c}}1&2&3\\{ - 2}&3&{ - 1}\\3&1&2\end{array}} \right]$ અને $I$ એ ત્રણ કક્ષાનો એકમ શ્રેણિક હોય, તો $({A^2} + 9I)$ = . . . .
A
$2A$
B
$4A$
C
$6A$
D
એકપણ નહી.
Solution
(d) $A = \left[ {\begin{array}{*{20}{c}}1&2&3\\{ – 2}&3&{ – 1}\\3&1&2\end{array}} \right]$ ==> $A.A = {A^2} = \left[ {\begin{array}{*{20}{c}}6&{11}&7\\{ – 11}&4&{ – 11}\\7&{11}&{12}\end{array}} \right]\,,$
$I = \left[ {\begin{array}{*{20}{c}}1&0&0\\0&1&0\\0&0&1\end{array}} \right]$,then, ${A^2} + 9I = \,\left[ {\begin{array}{*{20}{c}}{15}&{11}&7\\{ – 11}&{13}&{ – 11}\\7&{11}&{21}\end{array}} \right]$.
Standard 12
Mathematics