问题描述: 已知A=3x³-2x²-5,B=5x³-3x²+8-1 (1)求3A-2B (2)求B-2A 1个回答 分类:数学 2014-11-25 问题解答: 我来补答 B=5x³-3x²+8-1 3A=3(3x³-2x²-5)2B=2(5x³-3x^2+7)3A-2B=9x^3-6x^2-15-10x^3+6x^2-14=-x^3-29B-2A=5X^3-3X^2+8-1-2(3X^3-2X^2-5)=-X^3+X^2+12 再问: 呀呀呀!错了!B=8x-1 再答: B=8x-1? 还是B=5x³-3x²+8x-1?再问: 是B=5x³-3x²+8x-1? 再答: 3A=3(3x³-2x²-5) 2B=2(5x³-3x^2+8x-1) 3A-2B=9x^3-6x^2-15-10x^3+6x^2-16x+2=-x^3-16x-13 B-2A=5X^3-3X^2+8x-1-2(3X^3-2X^2-5)=-X^3+X^2+8x+4 展开全文阅读