# Polynomial Probability

Author: mathforces
Problem has been solved: 20 times

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Let $f (x) = x ^ 2-3x-9$ be given. Nil chose a certain number $a$ in the interval from 5 (inclusive) to 15 (inclusive). Let $p$ be the probability that $[\sqrt {f(a)}] = \sqrt{f ([a])}$. What is $[2020p]$ equal to?