`@``text{Bơ}`

`1.`

`a) 7/-2 . 4/9 - 7/2 . 5/3`

`= -7/2 . (4/9 + 5/3)`

`= -7/2 . (4/9 + 15/9)`

`= -7/2 . 19/9`

`= -133/18`

`b) -48/81 . 125/32 . 16/-15`

`= -16/27 . (125/32 . -16/15)`

`= -16/27 . -25/6`

`= 400/162`

`= 200/81`

`c) 0,75 - 3/4 . 2/5 + 0,2`

`= 0,75 - 3/10 + 0,2`

`= 0,75 - 0,3 + 0,2`

`= 0,45 + 0,2`

`= 13/20`

`d) 9/14 : -54/42 . 5/-27`

`= 9/14 . -42/54 . -5/27`

`= 9/14 . -7/9 . -5/27`

`= -1/2 . -5/27`

`= 5/54`

`2.`

`a) (3x - 1) . 4/7 = 4/7 - 1/14`

`(3x - 1) . 4/7 = 8/14 - 1/14`

`(3x - 1) . 4/7 = 1/2`

`3x - 1 = 1/2 : 4/7`

`3x - 1 = 1/2 . 7/4`

`3x - 1 = 7/8`

`3x = 7/8 + 1`

`3x = 7/8 + 8/8`

`3x = 15/8`

`x = 15/8 : 3`

`x = 15/8 . 1/3`

`x = 15/24`

Vậy `x = 15/24`

`b) (2x + 5)^2 = 9`

`(2x + 5)^2 = 3^2` hoặc `(2x + 5)^2 = (-3)^2`

`=> 2x + 5 = 3` hoặc `2x + 5 = -3`

`=> 2x = 3 - 5` hoặc `2x = -3 - 5`

`=> 2x = -2` hoặc `2x = -8`

`=> x = -2 : 2` hoặc `x = -8 : 2`

`=> x = -1` hoặc `x = -4`

Vậy `x in {-1; -4}`

`c) (4x - 8)(1 - 2x) = 0`

`TH1:`

`4x - 8 = 0`

`4x = 0 + 8`

`4x = 8`

`x = 8 : 4`

`x = 2`

`TH2:`

`1 - 2x = 0`

`2x = 1 - 0`

`2x = 1`

`x = 1 : 2`

`x = 1/2`

Vậy `x in {2; 1/2}`

`d) 8/x - 5/6 = 2/3`

`8 : x = 2/3 + 5/6`

`8 : x = 4/6 + 5/6`

`8 : x = 3/2`

`8 : x = 3/2`

`x = 8 : 3/2`

`x = 8 . 2/3`

`x = 16/3`

Vậy `x = 16/3`