Question

[νì ¢υộ¢ đờι ℓà инữиɢ иιềм đαυ]

Tính:

\(E=\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}\)

Answer 1

[Cuộn tròn lăn lốc]

E =16+112+120+130+142+156

E=\(\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+\dfrac{1}{5.6}+\dfrac{1}{6.7}+\dfrac{1}{7.8}\)

 E=\(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{1}-...+\dfrac{1}{7}-\dfrac{1}{8}\)

 E=\(\dfrac{1}{2}-\dfrac{1}{8}=\dfrac{3}{8}\)

Answer 2

[νì ¢υộ¢ đờι ℓà инữиɢ иιềм đαυ]

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