Exponential Functions Practice Test

An exponential function $$f$$ has the property that for any increase of 1 in the input variable $$x$$, the output $$f(x)$$ is multiplied by a factor of 4. Which of the following could be an expression for $$f(x)$$?

The function $$f$$ is given by $$f(x) = 2(3)^x$$, and the function $$g$$ is given by $$g(x) = -2(3)^x$$. Which statement best describes the relationship between the graphs of $$f$$ and $$g$$?