Okay, here we have this:
Considering the provided graph, we obtain the following:
Looking at the graph we can see that f(1)=4, and f(0)=1, so let's replace in the most common form of the equation (y=bˣ), to find "b":
b¹=4
b=4
So, according with this, finally we find that the equation of the exponential function whise graph is shown is y=4ˣ.