`|2x-5|=-4 `
Do giá trị tuyệt đối của `x` khác số âm `(x>0 )`
`=> x\in{∅}`
`TH2 : 2x-5 = 4 `
`2x = 4 +5 `
`2x = 9 `
`x=9 : 2 `
`x=9/2 `
vậy `x\in{1/2;9/2}`
`b) 1/3 - | 5/4 - 2x| = 1/4 `
`|5/4 - 2x | = 1/3 - 1/4 `
`|5/4 - 2x| = 1/12 `
`TH1 : 5/4 - 2x = 1/12 `
`2x = 5/4 - 1/12 `
`2x=15/12 - 1/12 `
`2x = 7/6 `
`x = 7/(6 ): (2) `
`x=7/12 `
`TH2 : 5/4 - 2x = -1/12 `
`2x = 5/4 - (-1)/12 `
`2x=4/3 `
`x=4/(3 ):(2)`
`x=2/3 `
vậy `x\in{7/12;2/3}`
`1/2 - |x+1/5 | = 1/3 `
`|x+1/5| = 1/2 - 1/3 `
`|x+1/5 | =1/6 `
`TH1 : x + 1/5 = 1/6 `
`x=1/6 - 1/5 `
`x=-1/30`
`TH2 : x + 1/5 = -1/6 `
`x= -1/6 + 1/5 `
`x=1/30`
vậy `x\in{±1/30}`
`d) 3/4 - | 2x +1 | = 7/8 `
`|2x + 1 | = 3/4 - 7/8 `
`|2x + 1 | =-1/8`
`TH1 : 2x+1 = -1/8`
DO `x>0`
nên `x\in{∅}`
