题目

已知． ⑴求的值；⑵求的值． 答案：解：⑴由，解得或=．    ∵,  ∴, ∴．  ⑵原式=,  ∴原式=. 根据表格里的内容，选择最佳答案。LucyI like sports. I have ten tennis balls, seven basketballs, four volleyballs and five soccer balls. I play tennis with my friends every day.MaryI have five baseballs, five volleyballs, two soccer balls. I like ping-pong. It's easy for me. I often play ping-pong with my classmates. I also have three ping-pong bats and lots of ping-pong balls.AliceI don't have any balls. I love sports, but I don't play them. I only watch them on TV.1.Lucy and Mary have volleyballs.A. four B. five C. eight D. nine2.Lucy plays every day.A. ping-pong B. tennis C. baseball D. soccer3.Mary doesn't have .A. volleyballs B. ping-pong ballsC. baseballs D. basketballs4. has two soccer balls.A. Mary B. Lucy C. Alice D. Mary and Lucy5.Alice .A. has no balls B. doesn't like sportsC. thinks ping-pong is easyD. plays sports with her classmates