Factorize the following expression : \(x(x^3 – y^3) + 3xy(x – y)\)

\[ x(x^3 – y^3) + 3xy(x – y) \] \[ = x(x – y)(x^2 + xy + y^2) + 3xy(x – y) \] \[ = (x – y)\left[x(x^2 + xy + y^2) + 3xy\right] \] \[ = (x – y)(x^3 + x^2y + xy^2 + 3xy) \]