Lời giải :
5,
`2|3x-1|+1=5`
`->2|3x-1|=4`
`->|3x-1|=2`
`->` \(\left[ \begin{array}{l}3x-1=2\\3x-1=-2\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=1\\x=-\dfrac{1}{3}\end{array} \right.\)
Vậy `x\in {1;-1/3}`
6,
`|x+1/4|-3/4=5%`
`->|x+1/4|-3/4=1/20`
`->|x+1/4|=1/20+3/4`
`->|x+1/4|=4/5`
`->` \(\left[ \begin{array}{l}x+\dfrac{1}{4}=\dfrac{4}{5}\\x+\dfrac{1}{4}=-\dfrac{4}{5}\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=\dfrac{11}{20}\\x=-\dfrac{21}{20}\end{array} \right.\)
Vậy `x \in {11/20;-21/20}`
7,
`6,5-9/4 : |x+1/3|=2`
`->9/4:|x+1/3|=6,5-2`
`->9/4:|x+1/3|=4,5`
`->|x+1/3|=9/4 : 4,5`
`->|x+1/3|=1/2`
`->` \(\left[ \begin{array}{l}x+\dfrac{1}{3}=\dfrac{1}{2}\\x+\dfrac{1}{3}=-\dfrac{1}{2}\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=\dfrac{1}{6}\\x=-\dfrac{5}{6}\end{array} \right.\)
Vậy `x \in {1/6;-5/6}`
8,
`3/2 + 4/5|x-3/4|=7/4`
`->4/5|x-3/4|=1/4`
`->|x-3/4|=1/4 : 4/5`
`->|x-3/4|=5/16`
`->` \(\left[ \begin{array}{l}x-\dfrac{3}{4}=\dfrac{5}{16}\\x-\dfrac{3}{4}=-\dfrac{5}{16}\end{array} \right.\)
`->` \(\left[ \begin{array}{l}x=\dfrac{17}{16}\\x=\dfrac{7}{16}\end{array} \right.\)
Vậy `x \in {17/16;7/16}`
