Xét `(x + 2).(x^2 + 2) = 0`
⇔ \(\left[ \begin{array}{l}x + 2 = 0\\x^2 + 2 = 0\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x =-2\\x^2 = - 2\end{array} \right.\)
`⇔ x = -2 `
Xét `x^3 - 4x = 0`
`⇔ x . (x^2 - 4) = 0`
⇔ \(\left[ \begin{array}{l}x =0\\x^2 -4= 0\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x =0\\x^2 = 4\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x =0\\x=2\\x=-2\end{array} \right.\)
Xét `3x^3 + x^2 = 0`
`⇔ x^2 . (3x + 1) = 0`
⇔ \(\left[ \begin{array}{l}x^2 =0\\3x+1=0\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=0\\3x=-1\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=0\\x = -1/3\end{array} \right.\)
(Chúc bạn học tốt)
