a/ \(x^3-3x^2-x+3\)
\(=\left(x^3-3x^2\right)-\left(x-3\right)\)
\(=x^2\left(x-3\right)-\left(x-3\right)\)
\(=\left(x-3\right)\left(x^2-1\right)\)
\(=\left(x-3\right)\left(x-1\right)\left(x+1\right)\)
b/ \(x^2y-2xy^2+y^3\)
\(=y\left(x^2-2xy+y^2\right)\)
\(=y\left(x-y\right)^2\)