`10) 3 . (x - 1/2)^3 = 81`

`(x- 1/2)^3 = 81: 3`

`(x - 1/2)^3 = 27`

`(x-1/2)^3 = 3^3`

`x - 1/2 = 3`

`x = 3 + 1/2`

`x =7/2`

Vậy `x = 7/2`

`11)  2 . (1/4 + x)^3 = (-27)/4`

`(1/4 + x )^3 = (-27)/4 : 2`

`(1/4 + x)^3 = (-27)/8`

`(1/4 + x)^3 = (-3/2)^3`

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

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

`x = -7/4`

Vậy `x= -7/4`

`12) (x + 1/2)^3: 3 = (-1)/81`

`(x + 1/2)^3 = (-1)/81 . 3`

`(x+1/2)^3 = (-1)/27`

`(x + 1/2)^3 = (-1/3)^3`

`x + 1/2 = -1/3`

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

`x = -5/6`

Vậy `x = -5/6`

`13) (2/3 - x)^2 = 1 : 4/9`

`(2/3 - x)^2 = 9/4`

`(2/3 - x)^2 = (3/2)^2 = (-3/2)^2`

`2/3 - x = 3/2` hoặc `2/3 - x = -3/2`

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

`x = 2/3 - 3/2`

`x = -5/6`

`TH2: 2/3 - x = -3/2`

`x = 2/3 + 3/2`

`x = 13/6`

Vậy `x \in {-5/6; 13/6}`

`14) (2x - 1/5)^2 + 16/25 = 1`

`(2x - 1/5)^2 = 1 - 16/25`

`(2x - 1/5)^2 = 9/25`

`(2x - 1/5)^2 = (3/5)^2 = (-3/5)^2`

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

`TH1: 2x - 1/5 = 3/5`

`2x = 3/5 + 1/5`

`2x = 4/5`

`x = 4/5 : 2`

`x = 2/5`

`TH2: 2x - 1/5 = -3/5`

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

`2x = -2/5`

`x = -2/5 : 2`

`x = -1/5`

Vậy `x \in {-1/5; 2/5}`

`15) (2/5 - 3x)^2 - 1/5 = 4/25`

`(2/5 - 3x)^2 = 4/25 + 1/5`

`(2/5 - 3x)^2 = 9/25`

`(2/5 - 3x)^2 = (3/5)^2 = (-3/5)^2`

`2/5 - 3x = 3/5` hoặc `2/5 - 3x = -3/5`

`TH1: 2/5 - 3x = 3/5`

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

`3x = -1/5`

`x = -1/5 : 3`

`x= -1/15`

`TH2: 2/5 - 3x = -3/5`

`3x = 2/5 + 3/5`

`3x = 1`

`x = 1 : 3`

`x = 1/3`

Vậy `x \in {-1/15; 1/3}`