Tìm x , biết:
a) \(x + 0,75 = \frac{2}{3}\).
b) \(\left| {\frac{1}{2} - x} \right| = \frac{4}{5}\).
a) Dựa vào quy tắc chuyển vế để tìm x.
b) Chia hai trường hợp: \(\frac{1}{2} - x = \frac{4}{5}\) hoặc \(\frac{1}{2} - x = \frac{{ - {\rm{ }}4}}{5}\).
a) \(x + 0,75 = \frac{2}{3}\)
\(\begin{array}{l}x + \frac{3}{4} = \frac{2}{3}\\x = \frac{2}{3} - \frac{3}{4}\\x = \frac{{ - 1}}{{12}}\end{array}\)
Vậy \(x = \frac{{ - 1}}{{12}}\).
b) \(\left| {\frac{1}{2} - x} \right| = \frac{4}{5}\) thì \(\frac{1}{2} - x = \frac{4}{5}\) hoặc \(\frac{1}{2} - x = \frac{{ - {\rm{ }}4}}{5}\).
TH1. \(\frac{1}{2} - x = \frac{4}{5}\)
\(\begin{array}{l}x = \frac{1}{2} - \frac{4}{5}\\x = \frac{{ - 3}}{{10}}\end{array}\)
TH2. \(\frac{1}{2} - x = \frac{{ - {\rm{ }}4}}{5}\)
\(\begin{array}{l}x = \frac{1}{2} + \frac{4}{5}\\x = \frac{{13}}{{10}}\end{array}\)
Vậy \(x \in \left\{ {\frac{{ - 3}}{{10}};\frac{{13}}{{10}}} \right\}\).