3 and 4 .Determinants and Matrices
easy

જો $A = \left[ {\begin{array}{*{20}{c}}i&0\\0&i\end{array}} \right]$ અને $B = \left[ {\begin{array}{*{20}{c}}0&{ - i}\\{ - i}&0\end{array}} \right]$, તો $(A + B)(A - B)$ = . ..

A

${A^2} - {B^2}$

B

${A^2} + {B^2}$

C

${A^2} - {B^2} + BA + AB$

D

એકપણ નહી.

Solution

(a) Here $AB = \left[ {\begin{array}{*{20}{c}}i&0\\0&i\end{array}} \right]\,\left[ {\begin{array}{*{20}{c}}0&{ – i}\\{ – i}&0\end{array}} \right] = \left[ {\begin{array}{*{20}{c}}0&1\\1&0\end{array}} \right]$

and $BA = \left[ {\begin{array}{*{20}{c}}0&{ – i}\\{ – i}&0\end{array}} \right]\left[ {\begin{array}{*{20}{c}}i&0\\0&i\end{array}} \right]\, = \left[ {\begin{array}{*{20}{c}}0&1\\1&0\end{array}} \right]$

Since $AB = BA,$ therefore $(A + B)(A – B) = {A^2} – {B^2}$.

Standard 12
Mathematics

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