Tìm x , biết: a) 8/ 5 − 3/ 5 : x = 0 , 4 ;
Giải thích
a) \(\frac{8}{5} - \frac{3}{5}:x = 0,4\)
\(\frac{3}{5}:x = \frac{8}{5} - \frac{2}{5} = \frac{6}{5}\)
\(x = \frac{3}{5}:\frac{6}{5}\)
\(x = \frac{3}{5}.\frac{5}{6} = \frac{1}{2}\)
Vậy \(x = \frac{1}{2}\).
b) \(\frac{{\left| {2x - 1} \right|}}{5} = \frac{1}{4}\)
\(4\left| {2x - 1} \right| = 5.1\)
\(\left| {2x - 1} \right| = \frac{5}{4}\)
Trường hợp 1:
\(2x - 1 = \frac{5}{4}\)
\(2x = \frac{5}{4} + 1\)
\(2x = \frac{9}{4}\)
\(x = \frac{9}{8}\)
Vậy \(x \in \left\{ {\frac{9}{8}; - \frac{1}{8}} \right\}\).
Trường hợp 2:
\(2x - 1 = - \frac{5}{4}\)
\(2x = - \frac{5}{4} + 1\)
\(2x = - \frac{1}{4}\)
\(x = - \frac{1}{8}\)