Factorize each of the following expressions:

$6 x y+6-9 y-4 x=(6 x y-4 x)+(6-9 y) \quad$ [Regrouping the expressions]

$=2 x(3 y-2)+3(2-3 y)$

$=2 x(3 y-2)-3(3 y-2)$       $[\because(2-3 y)=-(3 y-2)]$

$=(2 x-3)(3 y-2)$        $[$ Taking $(3 y-2)$ as the common factor $]$