g) `-1 - (3x - 7/9)^3 = 7`
`(3x - 7/9)^3 = -1 - 7`
`(3x - 7/9)^3 = -8`
`(3x - 7/9)^3 = (-2)^3`
`=> 3x - 7/9 = -2`
`3x = -2 + 7/9`
`3x = -11/9`
`x = -11/9 : 3`
`x = -11/27`
Vậy `x = -11/27`.
h) `(x + 1/5)^2 + 17/25 = 26/25`
`(x + 1/5)^2 = 26/25 - 17/25`
`(x + 1/5)^2 = 9/25`
`(x + 1/5)^2 = (-3/5)^2 = (3/5)^2`
`=> x + 1/5 = -3/5` hoặc `x + 1/5 = 3/5`
`=> x = -4/5` hoặc `x = 2/5`
Vậy `x ∈ {-4/5 ; 2/5}`.
i) `(2x + 1)(3x^3 + 375) = 0`
`=> 2x + 1 = 0` hoặc `3x^3 + 375 = 0`
+) `2x + 1 = 0`
`=> 2x = 1`
`=> x = 0,5`
+) `3x^3 + 375 = 0`
`=> 3x^3 = -375`
`=>x^3 = -125`
`=> x^3 = (-5)^3`
`=> x = -5`
Vậy `x ∈ {-5 ; 0,5}`.