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MathNet 2025-part-02 — 186 problems (EN–VI) Question 135

Math Olympiad Vault · MathNet 2025-part-02 — 186 problems (EN–VI)

Question 135

The set of points in 3-dimensional coordinate space that lie in the plane $x + y + z = 75$ whose coordinates satisfy the inequalities
$$
x - yz \lt y - zx \lt z - xy
$$
forms three disjoint convex regions. Exactly one of those regions has finite area. The area of this finite region can be expressed in the form $a\sqrt{b}$, where $a$ and $b$ are positive integers and $b$ is not divisible by the square of any prime. Find $a+b$.