\(2x^3+3x^2+6x+4=0\)
\(\Leftrightarrow2x^3+2x^2+4x+4+x^2+2x=0\)
\(\Leftrightarrow2x^2\left(x+1\right)+4\left(x+1\right)+x^2+2=0\)
\(\Leftrightarrow2\left(x+1\right)\left(x^2+2\right)+\left(x^2+2\right)=0\)
\(\Leftrightarrow\left(x^2+2\right)\left(2x+2+1\right)=0\)
\(\Leftrightarrow x^2+2=0\) hoặc \(2x+3=0\)
ta có \(x^2+2>0 \forall x\)
\(2x+3=0\) \(\Leftrightarrow x=-1.5\)
vậy \(S=\left\{-1.5\right\}\)
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