\(\Leftrightarrow\left\{{}\begin{matrix}x^3-y^3=16x-4y\\-4=5x^2-y^2\end{matrix}\right.\)
\(\Rightarrow-4\left(x^3-y^3\right)=4\left(4x-y\right)\left(5x^2-y^2\right)\)
\(\Leftrightarrow y^3-x^3=20x^3-4xy^2-5x^2y+y^3\)
\(\Leftrightarrow21x^3-5x^2y-4xy^2=0\)
\(\Leftrightarrow x\left(21x^2-5xy-4y^2\right)=0\)
\(\Leftrightarrow x\left(7x-4y\right)\left(3x+y\right)=0\)
\(\Rightarrow...\)