已知定义域为R的函数f(x)=$\frac{-2^x+a}{2^x+1}$是奇函数

（1）求a值；

（2）判断并证明该函数在定义域R上的单调性；

（3）若对任意的t∈R，不等式f（t²﹣2t）+f（2t²﹣k）＜0恒成立，求实数k的取值范围；

（4）设关于x的函数F（x）=f（4^x﹣b）+f（﹣2^x+1）有零点，求实数b的取值范围．

当3m+2n=4时，则8^m•4ⁿ=​____。

用所给动词的正确形式填空。
①My parents want me____ (stay) at home every night because it’s dangerous ou tside.
②—You look so sad today.     —I____ (argue) with my girlfriend last night.
③Lucy, what should I do? I need some money ____  (buy) some presents for my best friend.
④—I found it difficult ____ (get) to sleep in the night.
—You’d better____  (take) some sleeping pills.
⑤Lily is 1.7 meters tall. She is tall enough ____  (reach) the apples on the tree.
⑥Don’t ____ (compare) others with yourself, just ____  (work) hard.
⑦She has to____ (go) to see the doctor.

选择合适的搭配。

明亮的____    河水

干净的____    教室

清清的____    地面

洁白的____    话语

亲切的____    云朵