Tìm x biết \(0,25 - \left( {\frac{{ - 3}}{7} - \frac{2}{5}} \right)x = \frac{{ - 4}}{5}\)
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Lời giải:
Báo sai\(\begin{array}{l} 0,25 - \left( {\frac{{ - 3}}{7} - \frac{2}{5}} \right)x = \frac{{ - 4}}{5}\\ \frac{1}{4} - \left( {\frac{{ - 3}}{7} - \frac{2}{5}} \right)x = \frac{{ - 4}}{5}\\ \,\,\,\,\,\,\,\,\,\,\,\frac{1}{4} - \frac{{ - 29}}{{35}}x = \frac{{ - 4}}{5}\\ \,\,\,\,\,\,\,\,\,\,\frac{1}{4} + \frac{{29}}{{35}}x = \frac{{ - 4}}{5}\\ \,\,\,\,\,\,\,\,\,\,\,\frac{{29}}{{35}}x = \frac{{ - 4}}{5} - \frac{1}{4}\\ \,\,\,\,\,\,\,\,\,\,\,\frac{{29}}{{35}}x = \frac{{ - 21}}{{20}}\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = \frac{{ - 21}}{{20}}:\frac{{29}}{{35}}\\ \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,x = \frac{{ - 21}}{{20}}.\frac{{35}}{{29}} = \frac{{ - 147}}{{116}} \end{array}\)