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MathNet 2019-part-02 — 184 problems (EN–VI) Question 54

Math Olympiad Vault · MathNet 2019-part-02 — 184 problems (EN–VI)

Question 54

We say that a triple of integers $(x, y, z)$ is *nice* if $x$, $y$ and $z$ are positive integers, with $y \geq 2$, and $x^{2}-3 y^{2}=z^{2}-3$.

a) Find a nice triple $(x, y, z)$ with $x=5$ and one with $x=7$.

b) Show that for every odd $x \geq 5$ there exist at least two distinct nice triples $\left(x, y_{1}, z_{1}\right)$ and $\left(x, y_{2}, z_{2}\right)$.

c) Find some nice triple with $x$ even.