题目

已知数列的前项和是，且. （1）求数列的通项公式； （2）设，求适合方程的正整数的值. , 答案：（1），且 数列为等比数列． （2）由（1）可求得． 若则，阅读理解。      My mother moved a lot when she was growing up on account of Grandpa being in the army. She hated having to adjust to new schools and make new friends. That's why I thought she was joking when she put forward the idea of moving. But she was completely serious. "For just the two of us," my mother said, "an apartment in the city will suit our needs much better." Personally, I think she lost her mind. I guess I can understand why she would want to move, but what about me and what this house means to me?       I suppose if you looked at my house, you might think it was just another country house. But to me it isanything but standard. I moved into this house with my parents ten years ago. I can still remember that firstday like it was yesterday. The first thing I noticed was the big front yard. To me it seemed like an ocean ofgrass-couldn't wait to dive in. The backyard was full of gnarled (扭曲的, 粗糙的) and scary trees that talked on windy nights. But I grew to like them and the shadows they cast in my room. My father and I even built a small tree house, where I often go to remember all the wonderful time we had before Father's death.      This house is special-maybe only to me-but special nevertheless. It's the little seemingly insignificant thingsthat make this house so special to me; the ice-cold tile floors that make me tremble on midnight snake runs; the smell of my fathers pipe that still exists; the towering bookcases of my mother; the view outside my bedroom window.       This house bears too many memories, memories which would be lost if we gave it up. 1. Why did the author's mother decide to move? [     ]A. Because she hated the countryside. B. Because Grandpa was on constant move. C. Because Dad's death made her lose her mind. D. Because she thought a city flat more fit for them. 2. What impressed the author when she first moved into the house? [     ]A. The tree house B. The big treesC. The cold floorsD. The green grass 3. How did the author let us feel that the house was special to her? [     ]A. By arguing whether the house was standard. B. By explaining why the house suited their needs.C. By describing the small things related to her house.D. By comparing the differences between country and city life.  4. The author describes the house with _____. [     ]A. love B. responsibility C. promise D. enthusiasm