\(y\left(y-1\right)\left(y-2\right)-y^2+1=0\)
\(\Rightarrow y\left(y-1\right)\left(y-2\right)-\left(y-1\right)\left(y+1\right)=0\)
\(\Rightarrow\left(y-1\right)\left(y\left(y-2\right)-\left(y+1\right)\right)=0\)
\(\Rightarrow\left(y-1\right)\left(y^2-2y-y-1\right)=0\)
\(\Rightarrow\left(y-1\right)\left(y^2-3y-1\right)=0\)
\(\Rightarrow\orbr{\begin{cases}y-1=0\\y^2-3y-1=0\end{cases}\Rightarrow\orbr{\begin{cases}y=1\\y=-0,3027\end{cases}}}\)
\(y\left(y-1\right)\left(y-2\right)-\left(y-1\right)\left(y+1\right)=0.\)
\(\left(y-1\right)\left(y^2-2y-y-1\right)=0\)
\(\left(y-1\right)\left(y-\frac{3+\sqrt{13}}{2}\right)\left(y+\frac{3+\sqrt{13}}{2}\right)=0\)
\(y\in\left\{1;+-\frac{3+\sqrt{13}}{2}\right\}\)
