# $$\text{G.P}$$

Algebra Level 3

Let $$A = 1+r^a + r^{2a} + r^{3a} + \cdots$$, and
let $$B = 1+r^b + r^{2b} + r^{3b} + \cdots$$.

If $$|r| < 1$$, which of the following is equal to $$\dfrac ab$$?

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