c: \(\dfrac{1}{5}< =x< =2\dfrac{1}{5}\)
=>\(\left\{{}\begin{matrix}x-\dfrac{1}{5}>=0\\x-2\dfrac{1}{5}< =0\end{matrix}\right.\)
=>\(\left\{{}\begin{matrix}\left|x-\dfrac{1}{5}\right|=x-\dfrac{1}{5}\\\left|x-2\dfrac{1}{5}\right|=\dfrac{11}{5}-x\end{matrix}\right.\)
\(C=\left|2\dfrac{1}{5}-x\right|+\left|x-\dfrac{1}{5}\right|+8\dfrac{1}{5}\)
\(=\dfrac{11}{5}-x+x-\dfrac{1}{5}+8+\dfrac{1}{5}\)
\(=\dfrac{10}{5}+8+\dfrac{1}{5}=10+\dfrac{1}{5}=\dfrac{51}{5}\)
d: x>0
=>\(x+3\dfrac{1}{2}>\dfrac{7}{2}>0\)
=>\(\left|x+3\dfrac{1}{2}\right|=x+\dfrac{7}{2}\)
\(D=\left|x+3\dfrac{1}{2}\right|+\left|x\right|-3\dfrac{1}{2}\)
\(=x+\dfrac{7}{2}+x-\dfrac{7}{2}\)
=2x
