Lời giải:
b, `|-4/27| - 1 1/3 . x = 2/9`
`⇒ 4/27 - 4/3 . x = 2/9`
`⇒ 4/3 . x = 4/27 - 2/9`
`⇒ 4/3 . x = 4/27 - 6/27`
`⇒ 4/3 . x = -2/27`
`⇒ x = -2/27 : 4/3`
`⇒ x = -2/27 . 3/4`
`⇒ x = -1/18`
Vậy `x = -1/18`.
c, `(1/4 - x)^2 - 125% = 1 13/16`
`⇒ (1/4 - x)^2 - 5/4 = 29/16`
`⇒ (1/4 - x)^2 = 29/16 + 5/4`
`⇒ (1/4 - x)^2 = 29/16 + 20/16`
`⇒ (1/4 - x)^2 = 49/16`
`⇒ (1/4 - x)^2 = (7/4)^2 = ((-7)/4)^2`
`⇒ 1/4 - x = 7/4` hoặc `1/4 - x = (-7)/4`
`⇒ x = 1/4 - 7/4 = -3/2` hoặc `x = 1/4 + 7/4 = 8/4 = 2`
Vậy `x ∈ { -3/2 ; 2 }`.
