\(\left(2x+1\right)\left(x+1\right)^2\left(2x+3\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}2x+1=0\\\left(x+1\right)^2=0\\2x+3=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}2x=-1\\x^2+2x+1=0\\2x=-3\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{2}\\x=-1\\x=-\dfrac{3}{2}\end{matrix}\right.\)
Vậy \(S=\left\{-\dfrac{1}{2};-1;-\dfrac{3}{2}\right\}\)