`\text{(x+ 2)² + x (x +2) = 0}`
`\text{⇔ (x + 2) (x + 2) + x (x +2) = 0}`
`\text{⇔ (x + 2 + x) (x + 2) = 0}`
`\text{⇔ (2x + 2) (x + 2) = 0}`
`\text{⇔ 2 (x + 1) (x + 2) = 0}`
`⇔` \(\left[ \begin{array}{l}x + 1=0\\x + 2=0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x = -1\\x = -2\end{array} \right.\)
`\text{Vậy x ∈ {-1; -2}}`