2025 SSMO Team Round Problems/Problem 4

Problem

Let $P(x) = x^2 - ax + b$ be a quadratic with nonzero real coefficients. Given that $P(a)$ and $P(-b)$ are roots of $P(x),$ there exists a value of $c$ such that $P(c)$ is constant for all possible $P(x)$. Find $c$.

Solution