1: \(=\left(a+b\right)\left(x-1\right)\)
2: \(=a\left(x+y\right)+b\left(x+y\right)=\left(x+y\right)\left(a+b\right)\)
3: \(=\left(x+y\right)\left(a+2\right)\)
4: \(=\left(x+y\right)\left(a-2\right)\)
6: \(=-2\left(x+y\right)+a\left(x+y\right)=\left(x+y\right)\left(a-2\right)\)