1. 计算:
(1)$2a(b - 3)$; (2)$(x - 2y)(-\frac{4}{3}xy^{2})$;
(3)$-2a^{2}(a - 3ab)$; (4)$(-2a^{2})\cdot(3ab^{2} - 5ab^{3})$;
(5)$(3x^{2}-\frac{4}{3}y+\frac{1}{2})\cdot6xy$; (6)$(-2a)^{2}\cdot(3a^{2} - a - 1)$;
(7)$(2xy^{2})^{3} - 4xy(2x^{2}y^{5} + xy)$; (8)$-a^{2}(-2ab) + 3a(a^{2}b - 1)$;
(9)$x^{2}(x - 1) + 2x(x^{2} - 2x + 3)$; (10)$(-2xy)^{2}\cdot(3xy^{2}) - 3x(4x^{2}y^{4} - xy^{2})$.
答案：(1)2ab-6a (2)$-\frac{4}{3}x^{2}y^{2}+\frac{8}{3}xy^{3}$ (3)$-2a^{3}+6a^{3}b$
(4)$-6a^{3}b^{2}+10a^{3}b^{3}$ (5)$18x^{3}y-8xy^{2}+3xy$
(6)$12a^{4}-4a^{3}-4a^{2}$ (7)$-4x^{2}y^{2}$
(8)$5a^{3}b-3a$ (9)$3x^{3}-5x^{2}+6x$ (10)$3x^{2}y^{2}$
2. 先化简,再求值:$x^{2}(x - 1) - x(x^{2} + 2x - 6)$,其中$x = \frac{1}{2}$.
答案：解:原式$=x^{3}-x^{2}-x^{3}-2x^{2}+6x=-3x^{2}+6x$,
当$x=\frac{1}{2}$时,原式$=\frac{9}{4}$.
