Tính
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Bài 14*: Tính:
a) \( B = \left( -\frac{1}{2} \right) + \left( -\frac{1}{6} \right) + \left( -\frac{1}{12} \right) + \left( -\frac{1}{20} \right) + \left( -\frac{1}{30} \right) + \left( -\frac{1}{42} \right) + \left( -\frac{1}{56} \right) + \left( -\frac{1}{72} \right) + \left( -\frac{1}{90} \right); \)
b) \( D = \frac{5}{2.1} + \frac{4}{1.11} + \frac{3}{11.2} + \frac{1}{2.15} + \frac{13}{15.4}. \)
Bài 14*: Tính:
a) \( B = \left( -\frac{1}{2} \right) + \left( -\frac{1}{6} \right) + \left( -\frac{1}{12} \right) + \left( -\frac{1}{20} \right) + \left( -\frac{1}{30} \right) + \left( -\frac{1}{42} \right) + \left( -\frac{1}{56} \right) + \left( -\frac{1}{72} \right) + \left( -\frac{1}{90} \right); \)
b) \( D = \frac{5}{2.1} + \frac{4}{1.11} + \frac{3}{11.2} + \frac{1}{2.15} + \frac{13}{15.4}. \)