Question

Answer 1

\(\left(x+\dfrac{2}{5}\right)^2=\dfrac{9}{16}\\ =>\left(x+\dfrac{2}{5}\right)^2=\left(\dfrac{3}{4}\right)^2\\ TH1:x+\dfrac{2}{5}=\dfrac{3}{4}\\ =>x=\dfrac{3}{4}-\dfrac{2}{5}\\ =>x=\dfrac{7}{20}\\ TH2:x+\dfrac{2}{5}=-\dfrac{3}{4}\\ =>x=\dfrac{-3}{4}-\dfrac{2}{5}\\ =>x=-\dfrac{23}{20}\)

Answer 2

( x + 2/5 )^2 = 9/16

( x + 2/5)^2 = (3/4)^2

Chia làm 2 trường hợp :

+ Trường hợp 1 : 

x + 2/5 = 3/4

x = 3/4 - 2/5

x = 7/20

+ Trường hợp 2 :

x + 2/5 = -3/4

x = (-3/4) - 2/5

x = -23/20

Vậy x = {7/20; -23/20}