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MathNet 2016-part-04 — 184 problems (EN–VI) Question 10

Math Olympiad Vault · MathNet 2016-part-04 — 184 problems (EN–VI)

Question 10

Let $f: \mathbb{R} \to (0, \infty)$ be a continuous periodic function. Under the assumption that $2$ is a period of $f$, prove that:

a.
$$
\int_0^2 \frac{f(x+1)}{f(x)} \, dx \ge 2;
$$

b.
$$
\int_0^2 \frac{f(x+1)}{f(x)} \, dx = 2 \text{ if and only if } 1 \text{ is a period of } f.
$$