计算: (1)(-7x2-8y2)•(-x2+3y2)=_; (2)(3x-2y)(y-3x)-(2x-y)(3x+y)=_.
问题描述:
计算:
(1)(-7x2-8y2)•(-x2+3y2)=______;
(2)(3x-2y)(y-3x)-(2x-y)(3x+y)=______.
答
(1)(-7x2-8y2)•(-x2+3y2),=7x4-21x2y2+8x2y2-24y4,=7x4-13x2y2-24y4;(2)(3x-2y)(y-3x)-(2x-y)(3x+y),=3xy-9x2-2y2+6xy-(6x2+2xy-3xy-y2),=-9x2-2y2+9xy-6x2+xy+y2,=-15x2-y2+10xy....