Question

J=2/35+4/77+2/143+4/221+2/323+4/437+2/575

 

Answer 1

\(J=\frac{2}{35}+\frac{4}{77}+\frac{2}{143}+\frac{4}{221}+\frac{2}{323}+\frac{4}{437}+\frac{2}{575}\)

\(=\frac{2}{5\times7}+\frac{4}{7\times11}+\frac{2}{11\times13}+\frac{4}{13\times17}+\frac{2}{17\times19}+\frac{4}{19\times23}+\frac{2}{23\times25}\)

\(=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{17}+\frac{1}{17}-\frac{1}{19}+\frac{1}{19}-\frac{1}{23}+\frac{1}{23}-\frac{1}{25}\)

\(=\frac{1}{5}-\frac{1}{25}=\frac{5}{25}-\frac{1}{25}=\frac{4}{25}\)

Answer 2

bằng 4/25.nếu đúng cho mình nhoa<3

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