(11·钦州)先化简,再求值:(a+1)(a-1)+a (1-a),其中a=2012.
计算:6.1-3.7-4.9+1.8;
计算:-4.2+5.7-8.4+10;
计算:-8+12-16-23.
计算:-3-4+19-11;
计算:10-17+8;