\(a,3x^3-5x^2+8x-6=0\)
\(\Rightarrow3x^3-3x^2-2x^2+2x+6x+8=0\)
\(\Rightarrow3x^2\left(x-1\right)-2x\left(x-1\right)+6\left(x-1\right)=0\)
\(\Rightarrow\left(x-1\right)\left(3x^2-2x+6\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x-1=0\\3x^2-2x+6=0\end{matrix}\right.\)
\(\Rightarrow x=1\)
Vậy \(S=\left\{1\right\}\)
\(b,x^3-3x^2+6x-4=0\)
\(\Rightarrow x^3-3x^2+3x-1+3x-3=0\)
\(\Rightarrow\left(x-1\right)^3+3\left(x-1\right)=0\)
\(\Rightarrow\left(x-1\right)\left[\left(x-1\right)^2+3\right]=0\)
\(\Rightarrow\left(x-1\right)\left(x^2-2x+4\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x-1=0\\x^2-2x+4=0\end{matrix}\right.\)
\(\Rightarrow x=-1\)
Vậy \(S=\left\{-1\right\}\)
