Đáp án:
Có: \[\left\{\begin{matrix} (2x-1)^{2020}\ge 0 & \\ (y-\dfrac{2}{5})^{2020}\ge 0 & \\ |x+y+z|\ge 0 & \end{matrix}\right.\]
\[→(2x-1)^{2020}+(y-\dfrac{2}{5})^{2020}+|x+y+z|\ge 0\] \[\to \] Dấu "=" xảy ra $⇔x=\dfrac{1}{2};y=\dfrac{2}{5};z=\dfrac{-9}{10}$