Question
Evaluate the following determinant:
$$ det \left( \begin{matrix}4&6\\9&11\end{matrix} \right) $$Answer
$$ det \left( \begin{matrix}4&6\\9&11\end{matrix} \right) = -10 $$
Explanation
The determinant of 2x2 matrix is calculated as:
$$ \color{blue}{ det \left( \begin{matrix} a & b \\ c & d \end{matrix} \right) = a \cdot d - c \cdot b } $$In our case we have:
$$ det \left( \begin{matrix} \cssId{i00}{4} & \cssId{i01}{6} \\ \cssId{i10}{9} & \cssId{i11}{11} \end{matrix} \right) =
\cssId{u0}{4 \cdot 11} - \cssId{u1}{9 \cdot 6} = 44 - 54 = -10$$
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