\(4\left(2-x\right)^2+xy-2y\)
\(=\left(8-4x\right)\left(2-x\right)+y\left(x-2\right)\)
\(=\left(8-4x\right)\left(2-x\right)-y\left(2-x\right)\)
\(=\left(8-4x-y\right)\left(2-x\right)\)
\(4\left(2-x\right)^2+xy-2y=4\left(2-x\right)^2+y\left(x-2\right)=4\left(2-x\right)^2-y\left(2-x\right)=\left(2-x\right)\left(8-4x-y\right)\)