Bài 4. Tìm x, biết: a) \(\left( \frac{1}{3}x \right) \cdot \frac{2}{3} = \frac{1}{4} \cdot \frac{2}{5}\) b) \((x - 2019)^{2020} = 1\) c) \(\left|x - \frac{2}{5}\right| + \frac{3}{4} = \frac{11}{4}\) d) \((x - 2)^{2018} + \left|y^2 - 9\right|^{2020} = 0\)

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Bài 4. Tìm x, biết:
a) \(\left( \frac{1}{3}x \right) \cdot \frac{2}{3} = \frac{1}{4} \cdot \frac{2}{5}\)
b) \((x - 2019)^{2020} = 1\)
c) \(\left|x - \frac{2}{5}\right| + \frac{3}{4} = \frac{11}{4}\)
d) \((x - 2)^{2018} + \left|y^2 - 9\right|^{2020} = 0\)