The Value of a Dollar

    When I was nineteen, I had a job at a local bookstore. One night, a young couple came in and walked here and there looking for a book. They seemed ____ (be) the usual type to give mall ____ (worker) a hard time. When they went to pay ____ the book, the girl was a dollar or two short of ____ (buy) the book she wanted.

    She looked disappointed. I had a customer discount card and it was still active. I told the girl ____ (gentle), "Hang on, don't worry, you'll have the money to buy the book." I typed my password.

    She gave me a ____ (thank) smile. With a dollar left, she and her boyfriend left the store. I believed that I would never see ____ (they) again.

    I don't remember how long it was. ____ they did return later that evening just to bring me ____ beautiful card that said "It's people like you who make the world a better place to live in."

    I ____ (move) by the little girl and her boyfriend. In fact, they have also made the world a little brighter.

①若集合A={y|y=x﹣1}，B={y|y=x²﹣1}，则A∩B={（0，﹣1），（1，0）}；

② $y=\sqrt{x-3}+\sqrt{2-x}$ 是函数解析式；

③ $y=\frac{\sqrt{1-x^2}}{3-\left|3-x\right|}$ 是非奇非偶函数；

④设二次函数f（x）=ax²+bx+c（a≠0），若f（x₁）=f（x₂）（x₁≠x₂），则f（x₁+x₂）=c．