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MathNet 2021 — Part 11 Question 19

Math Olympiad Vault · MathNet 2021 — Part 11

Question 19

Let $n \ge 4$ be an integer. Find all positive real solutions to the following system of $2n$ equations:
$$
\begin{aligned}
a_1 &= \frac{1}{a_{2n}} + \frac{1}{a_2}, & a_2 &= a_1 + a_3, \\
a_3 &= \frac{1}{a_2} + \frac{1}{a_4}, & a_4 &= a_3 + a_5, \\
a_5 &= \frac{1}{a_4} + \frac{1}{a_6}, & a_6 &= a_5 + a_7, \\
\vdots & & \vdots & \\
a_{2n-1} &= \frac{1}{a_{2n-2}} + \frac{1}{a_{2n}}, & a_{2n} &= a_{2n-1} + a_1.
\end{aligned}
$$