1. The problem statement, all variables and given/known data Let f : R(real numbers) (arrow) (0,infinity) have the property that f ' (x) = f (x) for all x. Show that f is an increasing functions for all x. 2. Relevant equations 3. The attempt at a solution I know that if f ' (x) > 0 , where all of x belongs to a,b (not bounded) then f is strictly increasing on [a,b]. So i need to show that f(x) > 0 maybe? Any help/guidelines would be much appreciated.