lx+5l= l3x-2l .......

l`x+5`l `=` l`3x-2`l

`<=>` $\left[\begin{matrix} x+5=3x-2\\ x+5=2-3x\end{matrix}\right.$

`<=>` $\left[\begin{matrix} x-3x=-2-5\\ x+3x=2-5\end{matrix}\right.$

`<=>` $\left[\begin{matrix} -2x=-7\\ 4x=-3\end{matrix}\right.$

`<=>` $\left[\begin{matrix} x=\dfrac{-7}{-2}\\ x=\dfrac{-3}{4}\end{matrix}\right.$

`<=>` $\left[\begin{matrix} x=\dfrac{7}{2}\\ x=\dfrac{-3}{4}\end{matrix}\right.$

Vậy `S={7/2;-3/4}`