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Bài 2: a) $~x+\frac35=\frac{-2}7$ Ta có: $~x = \frac{-2}{7} - \frac{3}{5}$ Quy đồng mẫu số: $~x = \frac{-10}{35} - \frac{21}{35}$ $~x = \frac{-31}{35}$ b) $~x+4,56=13,78$ Ta có: $~x = 13,78 - 4,56$ $~x = 9,22$ c) $|x-2|=5$ Ta có hai trường hợp: - $x - 2 = 5$ $x = 5 + 2$ $x = 7$ - $x - 2 = -5$ $x = -5 + 2$ $x = -3$ d) $~2.|x+\frac15|-\frac13=\sqrt{\frac{ab}{25}}$ Ta có: $~2.|x+\frac15| = \sqrt{\frac{ab}{25}} + \frac13$ $~|x+\frac15| = \frac{\sqrt{\frac{ab}{25}} + \frac13}{2}$ Ta có hai trường hợp: - $x + \frac15 = \frac{\sqrt{\frac{ab}{25}} + \frac13}{2}$ $x = \frac{\sqrt{\frac{ab}{25}} + \frac13}{2} - \frac15$ - $x + \frac15 = -\frac{\sqrt{\frac{ab}{25}} + \frac13}{2}$ $x = -\frac{\sqrt{\frac{ab}{25}} + \frac13}{2} - \frac15$ Đáp số: a) $~x = \frac{-31}{35}$ b) $~x = 9,22$ c) $~x = 7$ hoặc $~x = -3$ d) $~x = \frac{\sqrt{\frac{ab}{25}} + \frac13}{2} - \frac15$ hoặc $~x = -\frac{\sqrt{\frac{ab}{25}} + \frac13}{2} - \frac15$