【单选题】听力原文: Hong Kong Disneyland opened on Monday with a total of 15,000 visitors. Visitors from the mainland are counted for one third of the total. Most were from Guangdong. According to a survey, more th...
【简答题】函数 f ( x )的定义域为 D ,若满足① f ( x )在 D 内是单调函数,②存在[ a , b ]? D ,使 f ( x )在[ a , b ]上的值域为[- b ,- a ],那么 y = f ( x )叫做对称函数,现有 f ( x )= - k 是对称函数,那么 k 的取值范围是________.