(1)(x+a)×(x+b); (2)(3x+7y)(3x-7y); (3)(3x+9)(6x+8); (4)(1/2x2y-2xy+y2)×3xy.

问题描述:

(1)(x+a)×(x+b);
(2)(3x+7y)(3x-7y);
(3)(3x+9)(6x+8);
(4)(

1
2
x2y-2xy+y2)×3xy.

(1)(x+a)×(x+b)=x2+ax+bx+ab;
(2)(3x+7y)(3x-7y)=9x2-49y2
(3)(3x+9)(6x+8)=18x2+24x+54x+72=18x2+78x+72;
(4)(

1
2
x2y-2xy+y2)×3xy.=
3
2
x3y2-6x2y2+3xy3