Question

Tính tổng s

S=1/1x3+1/2x4+1/3x5+............+1/7x9+1/8x10

Answer 1

\(S=\frac{1}{2}.\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{ }\right)\)

Answer 2

\(S=\frac{1}{2}\left(1-\frac{1}{3}+\frac{1}{2}-\frac{1}{4}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{7}-\frac{1}{9}+\frac{1}{8}-\frac{1}{10}\right)\)

\(S=\frac{1}{2}\left(1+\frac{1}{2}-\frac{1}{9}-\frac{1}{10}\right)\)

\(S=\frac{1}{2}\times\frac{58}{45}=\frac{29}{45}\)

Answer 3

29/45 là kết quả đúng 100%

Answer 4

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