\(\left(x+2\right)^4=81\)
\(\Rightarrow\left(x+2\right)^4=3^4\)
\(\Rightarrow\left[{}\begin{matrix}x+2=3\\x+2=-3\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=3-2\\x=-3-2\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=1\\x=-5\end{matrix}\right.\)
Vậy \(S=\left\{1;-5\right\}\)
\(\left(x+2\right)^4=81\\ \Leftrightarrow\left(x+2\right)^4=3^4\\ \Leftrightarrow\left[{}\begin{matrix}-x-2=3\\x+2=3\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=-5\\x=1\end{matrix}\right.\)
Vậy...
(x-2)^4=81
(x-2)^4=3^4
=>x-2=3
x=3+2
x=5
\(\)Vậy x=5
