e,
\(x^3-7x+6=0\)
\(\Leftrightarrow x^3+2x^2-3x-2x^2-4x+6=0\)
\(\Leftrightarrow x\left(x^2+2x-3\right)-2\left(x^2+2x-3\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x^2+2x-3\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x^2-x+3x-3\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x-1\right)\left(x+3\right)=0\)
\(\Leftrightarrow\left\{{}\begin{matrix}x-2=0\\x-1=0\\x+3=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=2\\x=1\\x=-3\end{matrix}\right.\)
Vật pt có tập nghiệm \(S\in\left\{1;2;-3\right\}\)
h. \(x^3-5x^3+4x=0\)
\(\Leftrightarrow-4x^3+4x=0\)
\(\Leftrightarrow-4x\left(x^2-1\right)=0\)
\(\Leftrightarrow-4x\left(x-1\right)\left(x+1\right)=0\)
\(\left\{{}\begin{matrix}-4x=0\\x-1=0\\x+1=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=\infty\\x=1\\x=-1\end{matrix}\right.\)
Vậy pt có tập nghiệm \(S\in\left\{\infty,1,-1\right\}\)
