Đáp án:
Giải thích các bước giải:
`b)`
`(1/3)^(2x-1) - (1/3)^2 = (-2)/27`
`(1/3)^(2x - 1) = (-2)/27 + (1/3)^2`
`(1/3)^(2x - 1) = (-2)/27 + 1/9`
`(1/3)^(2x - 1) = (-2)/27 + 3/27`
`(1/3)^(2x - 1) = 1/27`
`(1/3)^(2x - 1) = (1/3)^3`
`2x - 1 = 3`
`2x = 3 + 1`
`2x = 4`
`x = 4 : 2`
`x = 2`