函数$f\left(x\right)=\ln \frac{x}{x-1}+x^{\frac{1}{2}}$的定义域为(    )

已知函数f（x）=x²﹣x﹣2a

（1）若a=1，求函数f（x）的零点；

（2）若f（x）有零点，求a的范围．

增加：在缺词处加一个漏词符号（^），并在此符号下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1）每处错误及其修改均仅限一词。

2）只允许修改10处，多者（从第11处起）不计分。

3）必须按答题要求做题，否则不给分。

    Today is the happy day in this holiday. Although I was very tired, but I found myself in these busy days. I am afraid of taking a bus usual; the awful smell of the bus drives me mad, make me feel carsick. But today I did feel carsick. I can defeat carsickness finally. At night I went out with an old friend I ever liked him, but all of us were so busy with examinations at the high school that we hadn't been together. I was much surprised when I received his call that I could hardly believe my ears. At first, I think we would never meet before we graduated. Thank him for giving me a happy day!