# An algebra problem by Paola Ramírez

Algebra Level 3

The first four terms of an arithmetic sequence are $$a+b,a-b,ab$$ and $$\frac{a}{b}$$.

If the 5th term can be written as $$\dfrac mn$$, where $$m$$ and $$n$$ are coprime positive integers, find the value of $$m+n$$.

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