# For real

Algebra Level 3

Suppose $$f$$ is a continuous, positive real-valued function such that $$f(x + y) = f(x)f(y)$$ for all real $$x,y.$$

If $$f(8) = 3$$ then $$\log_{9}(f(2015)) = \dfrac{a}{b}$$, where $$a$$ and $$b$$ are positive coprime integers. Find $$a - b.$$

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