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