`2)`
`a) 4/5 - 3 | x| = 1/5`
`3|x| = 4/5 - 1/5`
`3 | x | = 3/5`
`|x|= 3/5 : 3`
`|x | = 1/5`
⇒ \(\left[ \begin{array}{l}x=\frac{1}{5}\\x=\frac{-1}{5}\end{array} \right.\)
Vậy `x ∈ { 1/5 ; -1/5}`
`b) 4x - 1/2 x + 3/5 x = 4/5`
`( 4 - 1/2 + 3/5) x = 4/5`
`41/10 x = 4/5`
`x = 4/5 : 41/10`
`x = 8/41`
Vậy `x = 8/41`
`c) ( 2x - 8) ( 10 - 5x) = 0`
⇒\(\left[ \begin{array}{l}2x-8=0\\10-5x=0\end{array} \right.\)
\(\left[ \begin{array}{l}2x=0+8\\5x=10-0\end{array} \right.\)
\(\left[ \begin{array}{l}2x=8\\5x=10\end{array} \right.\)
\(\left[ \begin{array}{l}x=8:2\\x=10 : 5\end{array} \right.\)
\(\left[ \begin{array}{l}x=4\\x=2\end{array} \right.\)
Vậy `x∈ { 4 ; 2}`
`d) 3/4 + 1/4|2x -1| = 7/2`
`1/4 |2x - 1| = 7/2 - 3/4`
`1/4 |2x - 1| = 11/4`
`|2x - 1| = 11/4 : 1/4`
`|2x - 1| = 11`
⇒ `+) 2x - 1 = 11`
`2x = 11 + 1`
`2x = 12`
`x = 12 : 2`
`x = 6`
`+) 2x - 1 = -11`
`2x = -11 + 1`
`2x = -10`
`x = -10 : 2`
`x = -5`
Vậy `x ∈ { 6 ; -5}`
