2 câu trả lời
Answer
`x^4 - x^3 - 3x - x^4 = 0`
`=> (x^4 - x^4) - x^3 - 3x = 0`
`=> -x^3 - 3x = 0`
`=> - (x^3 + 3x) = 0`
`=> -x . (x^2 + 3) = 0`
`=>` $\left[\begin{matrix} -x = 0\\ x^2 + 3 = 0\end{matrix}\right.$
`=>` $\left[\begin{matrix} x = 0\\ x^2 = 0 - 3\end{matrix}\right.$
`=>` $\left[\begin{matrix} x = 0\\ x^2 = -3 \ \text{(Vô lý)}\end{matrix}\right.$
Vậy `x = 0`
$\text{$x^{4}$ - $x^{3}$ - $3x^{}$ - $x^{4}$ = 0}$
⇔ $\text{( $x^{4}$ - $x^{4}$ ) - $x^{3}$ - $3x^{}$ = 0}$
⇔ $\text{$-x^{3}$ - $3x^{}$ = 0}$
⇔ $\text{$-x^{}$ . ( $x^{2}$ + 3 ) = 0}$
⇔ $\left[\begin{matrix} -x=0\\ x^{2} + 3 = 0\end{matrix}\right.$
⇔ $\left[\begin{matrix}x=0\\ x^{2} = -3 ( Vô lý )\end{matrix}\right.$
$\text{Vậy $x^{}$ = 0}$
