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