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2025 AMC 10A Question 18

AMC10 · 2025 AMC 10A

Question 18

The harmonic mean of a collection of numbers is the reciprocal of the arithmetic mean of the reciprocals of the numbers in the collection. For example, the harmonic mean of $4,$ $4,$ and $5$ is

$$
\frac{1}{\frac{1}{3}\left(\frac{1}{4} + \frac{1}{4} + \frac{1}{5}\right)} = \frac{30}{7}.
$$

What is the harmonic mean of all the real roots of the $4050$th degree polynomial

$$
\begin{gathered} \prod_{k=1}^{2025}(kx^2 - 4x - 3) \\ {}= (x^2 - 4x - 3) \\ \quad {}\cdot (2x^2 - 4x - 3) \\ \quad {}\cdot (3x^2 - 4x - 3)\cdots \\ \quad {}\cdot (2025x^2 - 4x - 3)? \end{gathered}
$$
  1. $-\dfrac{5}{3}$
  2. $-\dfrac{3}{2}$
  3. $-\dfrac{6}{5}$
  4. $-\dfrac{5}{6}$
  5. $-\dfrac{2}{3}$