2x4 - 6x3 + x2 + 6x - 3 = 0
=> 2x4 - 2x3 - 4x3 + 4x2 - 3x2 + 3x + 3x - 3 = 0
=> 2x3(x - 1) - 4x2(x - 1) - 3x(x - 1) + 3(x - 1) = 0
=> (x - 1)(2x3 - 4x2 - 3x + 3) = 0
=> (x - 1)(2x3 + 2x2 - 6x2 - 6x + 3x + 3) = 0
=> (x - 1)[2x2(x + 1) - 6x(x + 1) + 3(x + 1)] = 0
=> (x - 1)(x + 1)(2x2 - 6x + 3) = 0
\(\Rightarrow\left[{}\begin{matrix}x-1\\x+1\\2x^2-6x+3\end{matrix}\right.\) (2x2 - 6x + 3 vô nghiệm)
\(\Rightarrow\left[{}\begin{matrix}x=1\\x=-1\end{matrix}\right.\)
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