Answer:
(0, infinity)
Explanation:
Note that F(0) = (2/3)^0 = 1; the y-intercept is (0, 1).
Because 2/3 is between 0 and 1, this is a decaying exponential. As x increases F decreases towards y = 0, but never actually touches y = 0.
As x decreases (moves away from x = 0, to the left), F increases.
Thus, the range of F is (0, infinity).