Question

Tính:

\(\frac{1}{10}\) -\(\frac{1}{40}\)-\(\frac{1}{88}\)-\(\frac{1}{154}\)-\(\frac{1}{238}\)-\(\frac{1}{340}\)

 

Answer 1

Đặt A= \(\frac{1}{10}-\frac{1}{40}-..-\frac{1}{340}\)

A=\(\frac{1}{10}-\left(\frac{1}{5.8}+\frac{1}{8.11}+...+\frac{1}{17.20}\right)\)

3A= \(\frac{1}{10}-(\frac{3}{5.8}+...+\frac{3}{17.20})\)

3A=\(\frac{1}{10}-\left(\frac{1}{5}-\frac{1}{8}+...+\frac{1}{17}-\frac{1}{20}\right)\)

3A=\(\frac{1}{10}-\left(\frac{1}{5}-\frac{1}{20}\right)\)

3A=\(\frac{1}{10}-\frac{3}{20}\)

3A=\(-\frac{1}{20}\)

A=\(-\frac{1}{60}\)

ttiikk nha bạn

Answer 2

\(=\frac{1}{2.5}-\frac{1}{5.8}-...-\frac{1}{17.20}.\)

\(=\frac{1}{10}-\frac{1}{3}\left(\frac{3}{5.8}+\frac{3}{8.11}+...+\frac{3}{17.20}\right).\)

\(=\frac{1}{10}-\frac{1}{3}\left(\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{11}+...+\frac{1}{17}-\frac{1}{20}\right).\)

\(=\frac{1}{10}-\frac{1}{3}\left(\frac{1}{5}-\frac{1}{20}\right)\)

\(=\frac{1}{10}-\frac{1}{3}.\frac{3}{20}\)

\(=\frac{1}{20}\)

Answer 3

Hyền 2k7:

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Answer 4

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