答案
解:(1)原式=
a
2bc
3·4a
4b
4c
2=2a
6b
5c
5;
(2)原式=3x-6y-2;
(3)原式=(2x)
2-(3y)
2-(2x+3y)
2,
=4x
2-9y
2-(4x
2+9y
2+12xy),
=4x
2-9y
2-4x
2-9y
2-12xy,
=-18y
2-12xy;
(4)原式=2005×2005-2006×(2005-1),
=2005×2005-2006×2005+2006,
=2005×(2005-2006)+2006,
=1.
解:(1)原式=
a
2bc
3·4a
4b
4c
2=2a
6b
5c
5;
(2)原式=3x-6y-2;
(3)原式=(2x)
2-(3y)
2-(2x+3y)
2,
=4x
2-9y
2-(4x
2+9y
2+12xy),
=4x
2-9y
2-4x
2-9y
2-12xy,
=-18y
2-12xy;
(4)原式=2005×2005-2006×(2005-1),
=2005×2005-2006×2005+2006,
=2005×(2005-2006)+2006,
=1.