a) $(x - 4).(x + 2) = 0$
$\Leftrightarrow \left[ \begin{array}{l}x - 4 = 0\\x + 2 = 0\end{array} \right.$
$\Leftrightarrow \left[ \begin{array}{l}x = 4\\x = -2\end{array} \right.$
b) $4(x + 1) - (3x + 1) = 14$
$\Leftrightarrow 4x + 4 - 3x - 1 = 14$
$\Leftrightarrow x + 3 = 14$
$\Leftrightarrow x = 11$
c) $(x - 1).(x - 2) = 0$
$\Leftrightarrow \left[ \begin{array}{l}x - 1 = 0\\x - 2 = 0\end{array} \right.$
$\Leftrightarrow \left[ \begin{array}{l}x = 1\\x = 2\end{array} \right.$
d) $-x.(x + 2) = 0$
$\Leftrightarrow \left[ \begin{array}{l}-x = 0\\x + 2 = 0\end{array} \right.$
$\Leftrightarrow \left[ \begin{array}{l}x = 0\\x = -2\end{array} \right.$
