Question

\(4x^2+4x+1=0\)

Answer 1

\(\left(2x+1\right)^2=0\\ 2x+1=0\\ 2x=-1\\ x=-\dfrac{1}{2}\)

Answer 2

\(4x^2+4x+1=0\)

\(\Leftrightarrow\left(2x+1\right)^2=0\)

\(\Leftrightarrow2x+1=0\)

\(\Leftrightarrow2x=-1\Leftrightarrow x=-\dfrac{1}{2}\)

Vậy \(S=\left\{-\dfrac{1}{2}\right\}\)