Đáp án:

 

Giải thích các bước giải:

 `a`

`2/11 * 3/8 + 2/11 : 8/5 + (-1)^19/11`

`=2/11 * 3/8 + 2/11 * 5/8 + (-1)/11`

`=2/11 * (3/8 + 5/8) -1/11`

`=2/11 *1-1/11`

`=1/11`

`b`

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

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

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

`=-1 +0 +0`

`=-1`

`c`

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

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

`=0`

`d`

`[(x-1/2)^2-6/25]*2=2^2/5`

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

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

`(x-1/2)^2 = (+-4/5)^2`

`x-1/2=4/5` hoặc `x-1/2 =-4/5`

`x=4/5 +1/2` hoặc `x=-4/5 +1/2`

`x=13/10` hoặc `x=-3/10`

Vậy `x in {13/10;-3/10}`