Tính: a, C = $\frac{1}{2.3.4}$ + $\frac{1}{3.4.5}$ + ….+ $\frac{1}{22.23.24}$ b, S = $\frac{1}{3 mũ 2}$ + $\frac{3}{3 mũ 3}$ + ….+ $\fra

0 bình luận về “Tính: a, C = $\frac{1}{2.3.4}$ + $\frac{1}{3.4.5}$ + ….+ $\frac{1}{22.23.24}$ b, S = $\frac{1}{3 mũ 2}$ + $\frac{3}{3 mũ 3}$ + ….+ $\fra”

1. a) $\ \dfrac{1}{2.3.4} +\dfrac{1}{3.4.5} +…+ \dfrac{22.23.24}$

   $ = \dfrac{1}{2}(\dfrac{2}{2.3.4} \dfrac{2}{3.4.5} + …+\dfrac{22.23.24} $

   $\ = \dfrac{1}{2}(\dfrac{1}{2.3} – \dfrac{1}{3.4} + \dfrac{1}{3.4} – \dfrac{4.5} + …+\dfrac{22.23} – \dfrac{1}{23.24}$

   $\ = \dfrac{1}{2}(\dfrac{1}{6} – \dfrac{1}{552}$

   $\ = \dfrac{91}{552}$

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