⑴f(x)在[m,n]上是单调的;
⑵当定义域是[m,n]时,f(x)的值域也是[m,n],则称[m,n]是该函数的“和谐区间”.若函数f(x)= a+1a ﹣ 1x (a>0)存在“和谐区间”,则实数a的取值范围是____.
Don't be ____ (暴露于) to the strong sunlight, which may damage your skin.
人体心脏内的瓣膜能够防止血液倒流,正常情况下血液不可能的流动方向是( )
I have some____(果汁).