Đáp án:
`e, x=(65)/8`
`f, x \in {4/3;2/9}`
Giải thích các bước giải:
`e, 3x - |x+15| =5/4 `
`<=> |x+15| = 3x -5/4`
`( ĐK: \ 3x -5/4 ≥0 <=> x ≥ 5/(12))`
TH1: `x+15=3x -5/4`
`<=> 3x -x = 15+5/4`
`<=> 2x = (65)/4`
`<=> x= (65)/8 \ (TM)`
TH2: `-(x+15) = 3x -5/4`
`<=> -x -15=3x -5/4`
`<=> 3x +x= -15 +5/4`
`<=> 4x = -(55)/4`
`<=> x = -(55)/(16) \ (KTM)`
Vậy `x= (65)/8`
`f, |2x-1| - |x +1/3| =0`
`<=> |2x -1| = |x+1/3|`
`<=>`\(\left[ \begin{array}{l}2x -1 = x+ \dfrac13\\2x -1 = -(x+\dfrac13)\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}2x -x = \dfrac 13 +1\\2x +x = -\dfrac13+1\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=\dfrac43\\3x = \dfrac23\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=\dfrac43\\x = \dfrac29\end{array} \right.\)
Vậy `x \in {4/3;2/9}`
