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Question
If A = [aij] =`[[2,3,-5],[1,4,9],[0,7,-2]]`and B = [bij] `[[2,-1],[-3,4],[1,2]]`
then find (i) a22 + b21 (ii) a11 b11 + a22 b22
Solution
\[\left( i \right)\]\[a_{22} + b_{21}\]\[\]
\[Here, \]
\[ a_{22} =4\text{ and }b _{21}= - 3 \]
\[ \Rightarrow a_{22} + b_{21} = 4 - 3 = 1\]
\[\left ( ii \right)\]
\[\]\[a_{11} b_{11} + a_{22} b_{22}\]
here
`a_11=2, b_11=2,a_22=4` and `b_22=4`\[ \Rightarrow a_{11} b_{11} + a_{22} b_{22} = 2 \times 2 + 4 \times 4\]
\[ \Rightarrow a_{11} b_{11} + a_{22} b_{22} = 4 + 16\]
\[ \Rightarrow a_{11} b_{11} + a_{22} b_{22} = 20\]
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