`4,`

`( 3x + 2 )( 5 - x^2 ) = 0`

`TH1:`
`3x + 2 = 0`

`=> 3x = 0 - 2`

`=> 3x = - 2`

`=> x = - 2 : 3`

`=> x = - 2/3`

`TH2:`
`5 - x^2 = 0`

`=> x^2 = 5 - 0`

`=> x^2 = 5`

`=> x = +- \sqrt{5}`

`=> x = { \sqrt{5} ; - \sqrt{5}}`

Vậy `x in { -2/3 ; \sqrt{5} ; - \sqrt{5}}`

`5,`

`| x - 1 | - | 2/3 - 3/4 | = 2`

`=> | x - 1 | - | - 1/12| = 2`

`=> | x - 1 | - 1/12 = 2`

`=> | x - 1 | = 2 + 1/12`

`=> | x - 1 | = 25/12`

`TH1:`
`x - 1 = 25/12`

`=> x = 25/12 + 1`

`=> x = 37/12`

`TH2:`

`x - 1 = - 25/12`

`=> x = - 25/12 + 1`

`=> x = - 13/12`

Vậy `x in { 37/12 ; - 13/12 }`

`6,`

`| x - 2/3 | - 2/5 = 1/3`

`=> | x - 2/3 | = 1/3 + 2/5`

`=> | x - 2/3 | = 11/15`

`TH1:`
`x - 2/3 = 11/15`

`=> x = 11/15 + 2/3`

`=> x = 7/5`

`TH2:`

`x - 2/3 = - 11/15`

`=> x = - 11/15 + 2/3`

`=> x = - 1/15`

Vậy `x in { 7/5 ; - 1/15 }`

`7,`

`| x - 2 | - | 1 - 2x | = 0`

`=> | x - 2 | = | 1 - 2x |`

`TH1:`
`x - 2 = 1 - 2x`

`=> x + 2x = 1 + 2`

`=> 1x + 2x = 3`

`=> 3x = 3`

`=> x = 3 : 3`

`=> x = 1`

`TH2:`
`x - 2 = - ( 1 - 2 x )`

`=> x - 2 = - 1 + 2x`

`=> x - 2x = - 1 + 2`

`=> 1x - 2x = 1`

`=> - 1x = 1`

`=> x = 1 : ( - 1 )`

`=> x = - 1`

Vậy `x in { 1 ; - 1 }`
`#`Nguyencanhthinh`#`
`*** Hoidap247`