Đáp án:
$\begin{array}{l}
{\left( {x - 2019} \right)^2} = {y^4} - 6{y^3} + 11{y^2} - 6y\\
\Rightarrow {\left( {x - 2019} \right)^2} = {y^4} - 6{y^3} + 9{y^2} + 2{y^2} - 6y\\
\Rightarrow {\left( {x - 2019} \right)^2} = {y^2}{\left( {y - 3} \right)^2} + 2y\left( {y - 3} \right)\\
\Rightarrow {\left( {x - 2019} \right)^2} = {\left( {y\left( {y - 3} \right) + 1} \right)^2} - 1
\end{array}$