9.

a, `-2/3 + 5/12`

`= -8/12 + 5/12`

`= -3/12 `

`= -1/4`

b, `75% - 1 1/2 + 0,5 : 5/12`

`= 3/4 - 3/2 + 1/2 * 12/5`

`= 3/4 - 3/2 + 12/10`

`= 9/20`

c, `5,36 * 12,34 + (-5,36) * 2,34`

`= 5,36 *(12,34 - 2,34)`

`= 5,36 * 10`

`= 53,6`

10. 

a, `x + 30% = -1,3`

`x + 3/10 = -13/10`

`x = -13/10 - 3/10`

`x= -16/10`

`x = -8/5`

b, `1 -(2x + 1/2)^2 = 16/25`

` -(2x + 1/2)^2 = 16/25 -1`

` -(2x + 1/2)^2 = -9/25`

`=> (2x + 1/2)^2 = 9/25

` 2x + 1/2 = ±3/5`

TH1: `2x + 1/2 = 3/5`

`2x  = 3/5 - 1/2`

`2x = 1/10`

`x = 1/20`

TH2:`2x + 1/2 = -3/5`

`2x + 1/2 = -3/5`

`2x = -3/5 - 1/2`

`2x = -11/10`

`x = -11/20`

c, `-3/2 + 5/7 + (-31/14) + 3 ≤ x ≤ 1/2 + 1/3 + 1/6 (x ∈ Z)`

` -21/14 + 10/14 - 31/14 + 42/14 ≤ x ≤ 3/6 + 2/6 + 1/6`

` 0/14 ≤ x ≤ 6/6`

`0 ≤ x ≤ 1`

`=> x ∈ (0;1)`

Vậy ..............

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