Đáp án:

Giải thích các bước giải:

 `a)`

` x/(- 18) = (- 50)/x `

` x * x = ( - 18 ) * ( - 50 ) `

` x^2 = 900 `

` x^2 = ( +- 30 )^2`

` x = 30 ` hoặc `x = - 30` 

Vậy ` x = 30 ` hoặc ` x = - 30` 

``

`b)`

` ( x/2 - 2 1/3 )^3 = - 8/27 `

` ( x/2 - 2 1/3 )^3 = ( - 2/3 )^3 `

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

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

` x/2 = 5/3 `

` x = 10/3 `

Vậy ` x = 10/3 `

``

c)`

` ( x/3 - 3 1/4 )^2 - 6 7/9 = 2 2/9 `

` ( x/3 - 3 1/4 )^2 = 2 2/9 + 6 7/9 `

` ( x/3 - 3 1/4 )^2 = 9 `

` ( x/3 - 3 1/4 )^2 = ( +- 3 )^ 2 `

` x/3 - 3 1/4 = 3` hoặc `x/3 - 3 1/4 = - 3 `

``

`TH1`

` x/3 - 3 1/4 = 3 `

` x/3 = 25/4 `

` x = 75/4 `

``

`TH2`

` x/3 - 3 1/4 = - 3 `

` x/3 = - 3 + 3 1/4 `

` x/3 = 1/4 `

`x = 3/4 `

Vậy `x = 75/4` hoặc `x = 3/4 `

``

`d)`

` (2x - 1)/(- 5) = (x - 1)/2 `

` 2 ( 2x - 1 ) = - 5 ( x - 1 ) `

` 4x - 2 = - 5x + 5 `

` 4x + 5x = 5 + 2 `

` 9x = 7 `

` x = 7/9`

Vậy ` x = 7/9` 

``

e)`

` - 1/4x - 5 2/5 = - 2 4/5 `

` - 1/4x = - 2 4/5 + 5 2/5 `

` - 1/4x = 13/5 `

` x = 13/5 : ( - 1/4 ) `

` x = - 52/5 `

Vậy ` x = - 52/5` 

``

`f)`

` 1 5/8x - 4 5/6 = - 2 1/3 `

` 1 5/8x = - 2 1/3 + 4 5/6 `

` 1 5/8x = 5/2 `

` x = 20/13 `

Vậy ` x = 20/13 `