This is an exponential function. These types of functions have asymtotes. Asymtotes are when x or y is approaching a specific value, but it's not touching it. If you put your function in a graphing calculator, you will find that the y is approaching 0, but it's not quite touching it. What we're looking for, however is domain (x), and there are no asymtotes for x because as you can see, every value on the x axis has a y point. Therefore the domain is all real numbers.
