(1) Original formula = (x 2-2y 2) (x+2y)-2xy (x-y)

=x^3-2xy^2+2x^2y-4y^3-2x^2y+2xy^2

=x^3-4y^3

When x=-2 and y=- 1/2, the original formula = (-2) 3-4x (- 1/2) 3.

=-8+ 1/2

=- 15/2。

(2)(x- 1)^2+(x+3)(x-3)+(x-3)(x- 1)

=x^2-2x+ 1+x^2-9+x^2-4x+3

=3x^2-6x-5

=3(x^2-2x)-5

=3X2-5

=6-5

= 1。