`#3107.101107`
`(x + 1)^2 = 121`
`=> (x + 1)^2 = (+-11)^2`
\(\Rightarrow\left[{}\begin{matrix}x+1=11\\x+1=-11\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=11-1\\x=-11-1\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=10\\x=-12\end{matrix}\right.\)
Vậy, `x \in {10; -12}.`