Bài 5:

a) `81/16 = (3^4)/(2^4) = (3/2)^4`

b) `256/625 = (4^4)/(5^4) = (4/5)^4`

c) `0,008 = 0,2 . 0,2 . 0,2 = (0,2)^3`

Bài 6:

a) `(5/3)^3 . (5/3)^2 = (5/3)^(3+2) = (5/3)^5`

b) `(4/3)^4 . 16/9 = (4/3)^4 . (4/3)^2 = (4/3)^(4+2) = (4/3)^6`

c) `(18/7)^5 : (18/7)^3 = (18/7)^(5-3) = (18/7)^2`

d) `(13/6)^5 : 169/36 = (13/6)^5 : (13/6)^2 = (13/6)^(5-2) = (13/6)^3`

Bài 7:

a) `5^6 : 5^5 + (4/19)^0`

`= 5 + 1`

`= 6`

b) `(3/7)^21 : (1-40/49)^3`

`= (3/7)^21 : (9/49)^3`

`= (3/7)^21 : [(3/7)^2]^3`

`= (3/7)^21 : (3/7)^6`

`= (3/7)^15`

c) `3 . (2/3)^3 - ((-52)/3)^0 + 4/9`

`= 3 . 2/3 . (2/3)^2 - 1 + (2/3)^2`

`= (3 . 2/3 + 1) . 4/9 - 1`

`= (2 + 1) . 4/9 - 1`

`= 3 . 4/9 - 1`

`= 4/3 - 1` 

`= 1/3`