填空:(1)_____+11=27; (2)7+___=4; (3)(-9)+_____=9;(4)12+___=0; (5)(-8)+_____=-15; (6)_____+(-13)=-6;
用简便方法计算:39×37-13××34=_______.
计算:21×3.14-31×3.14=_________.
-15a2+5a=________(3a-1);
因式分解:km+kn=_________;
3a2-6ab+a=_________(3a-6b+1);