(x+1/2)^2=4/25 moi nghuoi lam ho em voi a

$( x+ \frac{1}{2} )^2 = \frac{4}{25}$ 

<=> $ \sqrt{ (x + \frac{1}{2} )^2 } = \sqrt{ \frac{4}{25} }$  

<=> $ | x+ \frac{1}{2}| = \frac{2}{5}$ 

* TH1: $ x+ \frac{1}{2} = \frac{2}{5}$ 

<=> $ x= \frac{-1}{10}$ 

* TH2: $ x+ \frac{1}{2} = \frac{-2}{5}$ 

<=> $ x= \frac{-9}{10}$ 

Vậy $ S= ( \frac{-1}{10}; \frac{-9}{10} )$