填一填。

12－____＝____

12－____＝____

13－____＝____

13－____＝____

 划船时，浆往后划，船就会向前运动，这是因为力的作用是____的．以船为参照物，岸上的树木是____的．​

下列词语中划线字注音完全正确的一项是（    ）

用括号内所给动词的适当形式填空，并将答案写在答题卡标有题号的横线上。
⑴We all love Mr Hu who is very kind and ____ (treat) us as his own children.
⑵____  you____ (hand) in the report today?
     Yes, I put it on your desk shortly after lunch .
⑶The cinema we used to go to____  (turn) into a hotel by the government in two years
⑷Timmy is active. He has many hobbies from____  (collect) stamps to outdoor-activities .
⑸The accident was so bad that all the doctors except Dr Li____  (save) the patients in danger at that time,
⑹He told us the boat would not float in the direction of wind if it____  (control).
⑺The old man was honoured for what he____  (do) for the poor since 10 years ago..
⑻The girl thought that her decision ____  (affect) her future study in college and job as well.

已知f（x）=xlnx，g（x）=﹣x²+ax﹣3．

（1）求函数f（x）在t，t+2（t＞0）上的最小值；

（2）对一切x∈（0，+∞），2f（x）≥g（x）恒成立，求实数a的取值范围；

（3）证明：对一切x∈（0，+∞），都有lnx＞$\frac{1}{e^x}$﹣$\frac{2}{ex}$成立．