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