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MathNet 2022-part-04 — 197 problems (EN–VI) Question 157

Math Olympiad Vault · MathNet 2022-part-04 — 197 problems (EN–VI)

Question 157

Let $A$ be one of two points of intersection of two unequal circles in the same plane. If two particles from $A$ move each on a circle in a clockwise direction with two uniform velocities until they return to point $A$ at the same instant. Prove that there is always a point in the plane that is equidistant from the two particles at any moment while they are in motion.

Problem:
Let the parabola $y = x^2 + px + q$ be given, which intersects coordinate axes in 3 different points. Consider the circumcircle of the triangle having vertices of these 3 points. Prove that there is a point that belongs to that circle, regardless of values $p$ and $q$. Find that point.