Đặt \(N\left(y\right)=0\)
\(\Leftrightarrow3y^2-5y+2=0\)
\(\Leftrightarrow3y^2-3y-2y+2=0\)
\(\Leftrightarrow3y\left(y-1\right)-2\left(y-1\right)=0\)
\(\Leftrightarrow\left(y-1\right)\left(3y-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}y-1=0\\3y-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}y=1\\3y=2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}y=1\\y=\frac{2}{3}\end{matrix}\right.\)
Vậy: \(S_{N\left(y\right)}=\left\{1;\frac{2}{3}\right\}\)