快,急 (18 19:39:29)2x3+6x2                              -4x2+8ax+2x                    -3ab+6abx-9aby (x+z)2-(y+z)2                                                     4x3y-9xy3

问题描述:

快,急 (18 19:39:29)
2x3+6x2                              -4x2+8ax+2x                    -3ab+6abx-9aby
 
(x+z)2-(y+z)2                                                     4x3y-9xy3

(1)=6+12=18 (2)=-8+(8a+2)x=-4+(4a+1)x (3)=-2x+3y (4)2x+2z-2y-2z=2x-2y (5)=12y-27y=-15y