$$ \LARGE det \begin{bmatrix} \color{black}a & \color{black}b \\\color{black}c &\color{black}d \end{bmatrix} = ad - bc$$

Got it !

Determinant of a matrix 2 x 2

$\LARGE det \begin{bmatrix}1 & 2\\3 & 4\end{bmatrix} = $	$\LARGE 1 \cdot 4 - 2 \cdot 3 = -2$
$\LARGE det\begin{bmatrix}1 & x \\0 & -2 \end{bmatrix} = $	$\LARGE -2 $
$\LARGE det\begin{bmatrix}x & y \\2x & 2y \end{bmatrix} = $	$\LARGE 0$