Tìm x , biết: f) 2 − trị tuyệt đối của( x − 2/ 5 )= − 1/ 2 ;
Giải thích
f) \(2 - \left| {x - \frac{2}{5}} \right| = - \frac{1}{2}\)
\(\left| {x - \frac{2}{5}} \right| = 2 - \left( { - \frac{1}{2}} \right)\)
\(\left| {x - \frac{2}{5}} \right| = \frac{5}{2}\)
TH1: \[x - \frac{2}{5} = \frac{5}{2}\]
\[x = \frac{5}{2} + \frac{2}{5}\]
\[x = \frac{{29}}{{10}}\].
TH2: \[x - \frac{2}{5} = - \frac{5}{2}\]
\[x = - \frac{5}{2} + \frac{2}{5}\]
\[x = - \frac{{21}}{{10}}\].
Vậy \[x \in \left\{ { - \frac{{21}}{{10}};\frac{{29}}{{10}}} \right\}\].