计算: (1)(-2a+3b)(-2a-3b) (2)(x+y-2)(x-y+2) (3)(3x-4y)2 (4)(2x-y-3)2.

问题描述:

计算:
(1)(-2a+3b)(-2a-3b)
(2)(x+y-2)(x-y+2)
(3)(3x-4y)2
(4)(2x-y-3)2

(1)原式=4a2-9b2
(2)原式=x2-(y-2)2=x2-y2+4y-4;
(3)原式=9x2-24xy+16y2
(4)原式=(2x-y)2-6(2x-y)+9=4x2-4xy+y2-12x+6y+9.