Answer :
(x-t)(x-t) = x^2 - 2xt + t^2
(x^2 - 2xt + t^2)(x - t) = x^3 - 2x^2t + xt^2 - xt^2 + 2xt^2 - t^3
=
x^3 - t^3 - 2x^2t + 2xt^2
(x^2 - 2xt + t^2)(x - t) = x^3 - 2x^2t + xt^2 - xt^2 + 2xt^2 - t^3
=
x^3 - t^3 - 2x^2t + 2xt^2