So you already have the graphing part down?
Basically, whenever you have a function where there's an "x" as your exponent (f(x) = b^x), we'll categorize them as "exponential functions".
Exponential functions modify your graph in two different ways, they can either make it increase exponentially or decrease exponentially.
If you see that your graph is gradually increasing across the x-axis, then you can say that the function is making your graph exponentially increase by a factor of "4".