$$\left. \begin{array} { l } { 2 x ^ { 2 } - 4 } \\ { 4 a b - 8 a c + 12 a d } \\ { x ( a + b ) - y ( a + b ) } \\ { x ^ { 2 } - y ^ { 2 } } \end{array} \right.$$
$4a\left(a+b\right)\left(b+3d-2c\right)\left(2-x^{2}\right)\left(x^{2}-y^{2}\right)$
$2\left(x^{2}-2\right),\ 4a\left(b+3d-2c\right),\ \left(x-y\right)\left(a+b\right),\ x^{2}-y^{2}$
