f(x) = (x -1)(x -2)(x -3) . . . . . by the zero-product rule. If a is a zero, x-a is a factor.
.. = (x^2 -x -2x +2)(x -3) . . . multiplying the first two factors
.. = (x^2 -3x +2)(x -3) . . . . . collecting terms
.. = x^3 -3x^2 -3x^2 +2x +9x -6 . . . . multiplying these factors
.. = x^3 -6x^2 +11x -6 . . . . . your polynomial in standard form
