已知函数. (Ⅰ)若,求的取值范围; (Ⅱ)在(Ⅰ)的条件下,求的最大值. 答案:(Ⅰ)由, ………2分 所以的取值范围是. ……………………………3分 (Ⅱ)由(Ⅰ)知, 由柯西不等式 ………………5分 所以. 当且仅当即时,取最大值. Compared with 2 million tons last year, our coal output has increased _____ three times; that is to say, our coal output has increased_____8 million tons this year. A. to; to B. to; by C. by; by D. by; to