Tính:

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a) \(2 \cdot \left( \frac{1}{2}x - \frac{1}{3} \right) \frac{3}{2} = \frac{1}{4}\)
b) \( \left( \frac{1}{2} + 2x \right)(2x - 3) = 0\)
c) \( \frac{1}{5.8} + \frac{1}{8.11} + \frac{1}{11.14} + \cdots + \frac{1}{x(x+3)} = \frac{101}{1540} \)