Sejam os números x \( ∈ \) \( \mathbb{R} \), y \( ∈ \) \( \mathbb{R} \), z \( ∈ \) \( \mathbb{R} \), dados por:

\( x = \dfrac{1}{2} + \dfrac{1}{6} + \dfrac{1}{12} + \dfrac{1}{20} + ... + \dfrac{1}{2019^2 - 2019} \)

\( y = \dfrac{2}{2} + \dfrac{2}{6} + \dfrac{2}{12} + \dfrac{2}{20} + ... + \dfrac{2}{2019^2 - 2019} \)

\( z = \dfrac{3}{2} + \dfrac{3}{6} + \dfrac{3}{12} + \dfrac{3}{20} + ... + \dfrac{3}{2019^2 - 2019} \)

O valor de \( \left ( x-\dfrac{y}{2} \right )^2 + \left ( \dfrac{z}{3} \right ) \)