计算:(1)-2xy(3x²y-4xy²);(2)(a-2b)(a²+2ab+4b²).

计算:(1)-2xy(3x²y-4xy²);(2)(a-2b)(a²+2ab+4b²).
计算:(1)-2xy(3x²y-4xy²);(2)(a-2b)(a²+2ab+4b²).

计算:(1)-2xy(3x²y-4xy²);(2)(a-2b)(a²+2ab+4b²).
:(1)-2xy(3x²y-4xy²);
=-6x^3y^2+8x^2y^3
(2)(a-2b)(a²+2ab+4b²).
=a^3+2a^2b+4ab^2-2a^2b-4ab^2-8b^3
=a^3-8b^3

(1)-2xy(3x²y-4xy²)
=-6x³y²+8x²y³

(2)(a-2b)(a²+2ab+4b²)
=a³-8b³

（1）原式=-6x³y²+8x²y³
（2）原式=（a-2b）（a+2b） 完全平方公式
=a²-4b² 平方差公式