(1/5)^x-2 + (1/5)^x-1= 6/25

Đáp án `+` Giải thích các bước giải:

 `(1/5)^(x-2) + (1/5)^(x-1) = 6/25`

`=> (1/5)^x : (1/5)^2 + (1/5)^x : 1/5 = 6/25`

`=> (1/5) ^x . 25 + (1/5)^x . 5 = 6/25`

`=> (1/5)^x . (25 + 5) = 6/25`

`=> (1/5)^x . 30 = 6/25`

`=> (1/5)^x = 6/25 : 30`

`=> (1/5)^x = 1/125`

`=> (1/5)^x = (1/5)^3`

`=> x= 3`