Giải giúp mình với ạ

Đáp án `+` Giải thích các bước giải:

1.

a) `(-9)/7 . (14/15 + 7/9)`

`= (-9)/7 . 14/15 + (-9)/7 . 7/9`

`= (-3) . 2/5 + (-1)`

`= (-6)/5 + (-5)/5`

`= (-11)/5.`

b) `(2/3 - 6/5) . 15/(-36)`

`= 2/3 . 15/(-36) - 6/5 . 15/(-36)`

`= 2/3 . (-15)/36 - 6/5 . (-15)/36`

`= (-5)/18 - (-3)/6`

`= (-5)/18 + 9/18`

`= 4/18 = 2/9.`

c) `(3/29 - 1/5) : 3/29`

`= (3/29 - 1/5) . 29/3`

`= 3/29  . 29/3 - 1/5 . 29/3`

`= 1 - 29/15`

`= 15/15 - 29/15`

`= (-14)/15.`

d) `((-2)/5 + 1/3) . (3/2 - 3/7)`

`= ((-6)/15 + 5/15) . (21/14 - 6/14)`

`= (-1)/15 . 15/14`

`= (-1)/14.`

e) (1/2 - 1/3) : (5 - 1/4)

= (3/6 - 2/6) : (20/4 - 1/4)

= 1/6 : 19/4

= 1/6 . 4/19

= 2/57.

f) `(4/5)^2 - ((-3)/7)^2`

`= 16/25 - 9/49`

`= 784/1225 - 225/1225`

`=  559/1225.`

2.

a) `(-5)/7 + 3/4 + (-1)/5 + (-2)/7 + 1/4`

`= ((-5)/7 + (-2)/7) + (3/4 + 1/4) + (-1)/5 `

`= (-7)/7 + 4/4 + (-1)/5 `

`= (-1) + 1 + (-1)/5 `

`= 0 + (-1)/5 `

`= (-1)/5.`

b) `31/23 - (7/32 + 8/23) `

`= 31/23 - 7/32 - 8/23`

`= (31/23 - 8/23) - 7/32`

`= 23/23 - 7/32`

`= 1 - 7/32`

`= 32/32 - 7/32`

`= 25/32.`

c) `38/45 - (8/45 - 17/51 - 3/11) `

`= 38/45 - 8/45 + 17/51 + 3/11`

`= (38/45 - 8/45) + (17/51 + 3/11)`

`= 30/45 + 20/51`

`= 2/3 + 20/51`

`= 102/153 + 60/153`

`= 162/153 = 54/51.`

d) `(1/3 + 12/67 + 13/41) - (79/67 - 28/41)`

`= 1/3 + 12/67 + 13/41 - 79/67 + 28/41`

`= (12/67 - 79/67) + (13/41 + 28/41) + 1/3`

`= (-67)/67 + 41/41 + 1/3`

`= (-1) + 1 + 1/3`

`= 0 + 1/3`

`= 1/3.`