Question

[Huỳnh Thanh Danh]

Đố mấy bạn 

A = \(\frac{7}{3.13}\) +\(\frac{7}{13.23}\) + \(\frac{7}{23.33}\) +\(\frac{7}{43.53}\) +\(\frac{7}{53.63}\)

Answer 1

[Phạm Nguyễn Tất Đạt]

A=\(\frac{7}{10}\)*(\(\frac{10}{3\cdot13}\)+\(\frac{10}{13\cdot23}\)+\(\frac{10}{23\cdot33}\)+\(\frac{10}{43\cdot53}\)+\(\frac{10}{53\cdot63}\))

A=\(\frac{7}{10}\)*(\(\frac{1}{3}\)-\(\frac{1}{13}\)+\(\frac{1}{13}\)-\(\frac{1}{23}\)+\(\frac{1}{23}\)-\(\frac{1}{33}\)+\(\frac{1}{43}\)-\(\frac{1}{53}\)+\(\frac{1}{53}\)-\(\frac{1}{63}\))

A=\(\frac{7}{10}\)*(\(\frac{1}{3}\)-\(\frac{1}{33}\)+\(\frac{1}{43}\)-\(\frac{1}{63}\))

A=\(\frac{7}{10}\)*(\(\frac{10}{33}\)+\(\frac{20}{2709}\))

A=\(\frac{7}{10}\)*\(\frac{9250}{29799}\)

A=\(\frac{925}{4257}\)

Answer 2

[Huỳnh Thanh Danh]

trình bày sai