\(...=\left(x^2-y^2\right)+\left(x-y\right)=\left(x-y\right)\left(x+y\right)+\left(x+y\right)=\left(x+y\right)\left(x-y+1\right)\)
\(=\left(x^2-y^2\right)+\left(x-y\right)\)
\(=\left(x-y\right).\left(x+y\right)+\left(x+y\right)\)
\(=\left(x+y\right)\left(x-y+1\right)\)
P/s: Tham khảo nha!!