\(-TH1:\left|x+\dfrac{1}{2}\right|=x+\dfrac{1}{2}\)
\(=>2.\left(x+\dfrac{1}{2}\right)=\dfrac{1}{5}\\ =>2x+1=\dfrac{1}{5}\\ =>2x=\dfrac{1}{5}-1\\ =>2x=\dfrac{-4}{5}\\ =>x=-\dfrac{2}{5}\)
\(-TH2:\left|x+\dfrac{1}{2}\right|=-x-\dfrac{1}{2}\)
\(=>2.\left(-x-\dfrac{1}{2}\right)=\dfrac{1}{5}\\ =>-2x-1=\dfrac{1}{5}\\ =>-2x=\dfrac{1}{5}+1\\ =>-2x=\dfrac{6}{5}\\ =>x=-\dfrac{3}{5}\)
Vậy \(S=\left\{-\dfrac{2}{5};-\dfrac{3}{5}\right\}\)

b./
c*./ 
b/
=
e/
=
và
e) 9x =81
h)
và x + y= -21 i)
và 3x - 2y = -2
và 3x – 2y – z = -29