Lt       [x]  is equal to.
 x→ 2^-

The value of 

If f (x)  = x when x2when x>0, then   f(x) is.

If f (2) = 4 and f' (2) = 4, then  equals.

     = 0  , [x]=0
Where [x] denotes the greatest integer ≤x, the    f(x) equals