`a) ( x - 1/3)^3 = (-8)/27`
`( x - 1/3)^3 = (-2/3)^3`
⇒ `x - 1/3 = -2/3`
`x = -2/3 + 1/3`
`x =-1/3`
Vậy `x = -1/3`
``
`a) ( 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`
``
`b) ( 5x + 1)^2 = 36/49`
`( 5x + 1)^2 = (+-6/7)^2`
⇒ `+)` trường hợp `1` :
`5x + 1 = 6/7`
`5x = 6/7 - 1`
`5x = -1/7`
`x = -1/7 : 5`
`x= -1/35`
`+)` trường hợp `2` :
`5x + 1 = -6/7`
`5x = -6/7 - 1`
`5x = -13/7`
`x = -13/7 : 5`
`x = -13/35`
Vậy `x ∈ { -1/35 ; -13/35}`
``
`b) ( 2x - 3)^2 = 4/25`
`(2x - 3)^2 = (+-2/5)^2`
⇒`+)` trường hợp `1` :
`2x - 3 = 2/5`
`2x = 2/5 + 3`
`2x = 17/5`
`x = 17/5 : 2`
`x= 17/10`
`+)` trường hợp `2` :
`2x - 3 = -2/5`
`2x = -2/5 + 3`
`2x = 13/5`
`x = 13/5 : 2`
`x =13/10`
Vậy `x ∈ {17/10 ; 13/10}`
``
`c) ( 1/2)^(2x - 1) = 1/8`
`( 1/2)^(2x - 1) = (1/2)^3`
⇒ `2x - 1 = 3`
`2x = 3 + 1`
`2x = 4`
`x = 4 : 2`
`x = 2`
Vậy `x = 2`
``
`c) (-1/3)^(x - 3) = 1/81`
`(-1/3)^(x - 3) = (-1/3)^4`
⇒ `x - 3 = 4`
`x = 4 + 3`
`x = 7`
Vậy `x = 7`