若{a_n}为递减数列，则{a_n}的通项公式可以为（  ）

已知函数f（x）=log₉（9^x+1）+kx（k∈R）是偶函数．

（1）求k的值；

（2）若方程f（x）=$\frac{1}{2}$x+b有实数根，求b的取值范围；

​（3）设h（x）=log₉（a•3^x﹣$\frac{4}{3}$a），若函数f（x）与h（x）的图象有且只有一个公共点，求实数a的取值范围．

    Many people like to watch TV, There are all kinds of programs on TV. The soap opera is one of them.

    The soap opera was first on the radio in the 1920s, then it started on TV in the 1940s. Why do so many people like to watch soap operas on TV, especially young people? What makes soap operas popular? Let's find out.

    First, what's happening in the soap opera is very different from our lives. Everything is perfect in the play, People don't need to worry about almost anything. People don't have more Problems.

    Second, there are many beautiful girls and handsome boys in the soap opera. They are cool. They make young people crazy. They make young people happy.

    Third, the story in the soap opera is usually interesting. It makes people relaxed after a day's hard work. Even some old people like to watch it, too.

    But some people don't like it, they think the show is too slow and too long. Do you like to watch soap operas? What do you think of them?