(1)原式=-2a 2b+
5
3 ac 2+1;
(2)原式=9(x 2-4)-(9x 2-12x+4)=9x 2-36-9x 2+12x-4=12x-40;
(3)原式=2005 2-(2005-1)×(2005+1)=2005 2-(2005 2-1)=1;
(4)原式=3-1-9+
1
8 =-6
7
8 .
(1)原式=-2a 2b+
5
3 ac 2+1;
(2)原式=9(x 2-4)-(9x 2-12x+4)=9x 2-36-9x 2+12x-4=12x-40;
(3)原式=2005 2-(2005-1)×(2005+1)=2005 2-(2005 2-1)=1;
(4)原式=3-1-9+
1
8 =-6
7
8 .