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If A=\(\begin{bmatrix}1&3\\2&1\end{bmatrix}\), then ________(a) |2A|=4|A|(b) |2A|=2|A|(c) |A|=2|A|(d) |A|=|4A|This question was posed to me by my school teacher while I was bunking the class.Question is from Properties of Determinants in portion Determinants of Mathematics – Class 12

Answer» RIGHT choice is (a) |2A|=4|A|

Easiest explanation: Given that, A=\(\begin{BMATRIX}1&3\\2&1\end{bmatrix}\)

2A=2\(\begin{bmatrix}1&3\\2&1\end{bmatrix}\)=\(\begin{bmatrix}2&6\\4&2\end{bmatrix}\)

|2A|=\(\begin{vmatrix}2&6\\4&2\end{vmatrix}\)=(4-24)=-20

4|A|=4\(\begin{vmatrix}1&3\\2&1\end{vmatrix}\)=4(1-6)=4(-5)=-20

∴|2A|=4|A|.


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