Bshsjw90102029202001010100101091

$#gialong209$

`a) x^3 - 0,25x = 0`

`<=> x^3 - 1/4 x = 0`

`<=> x(x^2 - 1/4) = 0`

`<=>` $\left[\begin{matrix} x = 0\\ x^2 = \dfrac{1}{4}\end{matrix}\right.$

`<=>` $\begin{cases} x = 0\\ x = \dfrac{1}{2}\\x = \dfrac{- 1}{2} \end{cases}$

Vậy : `S = {0 ; 1/2 ; - 1/2}`

`b) x^2 - 10x = - 25`

`<=> x^2 - 10x + 25 = 0`

`<=> (x - 5)^2 = 0`

`<=> x - 5 = 0`

`<=> x = 5`

Vậy : `S = { 5 }`