# João's functional equation

Algebra Level 2

Let $$f$$ be a function from the positive integers to the positive integers that satisfies the property $f (x + y) = f (x) f (y)$

for all pairs of positive integers $$(x,y)$$. If we are given that $$f(2) = 9$$, what is the value of $$f(5)$$?

This problem is posed by João B.

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