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呀呀呀！错了！B=8x-1B=8x-1?还是B=5x³-3x²+8x-1?是B=5x³-3x²+8x-1?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-13B-2A=5X^3-3X^2+8x-1-2(3X^3-2X^2-5)=-X^3+X^2+8x+4