This Problem is from GMAT Prep, plz help me solve it:
For which of the following functions is f(a+b) = f(a)+f(b) for all positive numbers a and b?
A: f(x) = x^2
B: f(x) = x+1
C: f(x) = Root of x
D: f(x) = 2/x
E: f(x) = -3x
OA is (E)
For which of the following functions is f(a+b) = f(a)+f(b) for all positive numbers a and b?
A: f(x) = x^2
B: f(x) = x+1
C: f(x) = Root of x
D: f(x) = 2/x
E: f(x) = -3x
OA is (E)
