[Toán Học]
`@` Xu FF
`@` Gửi ạ <3
$A = \dfrac{5}{1 · 6} - \dfrac{5}{6 · 11} - \dfrac{5}{11 · 16} - ...... - \dfrac{5}{2006 · 2011}$
`=> A =` $\dfrac{5}{1 · 6}$ ` - ( 5/(6 · 11) + 5/(11 · 16) + ..... + 5/(2006 · 2011) ) `
`=> A =` $\dfrac{5}{1 · 6}$ ` - ( 1/6 - 1/11 + 1/11 - 1/16 + .... + 1/2006 - 1/2011 ) `
`=> A =` $\dfrac{1}{1}$ ` - 1/6 - ( 1/6 - 1/2011 ) `
`=> A =` $\dfrac{1}{1}$ ` - 1/6 - 1/6 + 1/2011 `
`=> A =` $\dfrac{1}{1}$ ` - 1/3 + 1/2011 `
`=> A =` $\dfrac{2}{3}$ ` + 1/2011 `
`=> A =` $\dfrac{4025}{6033}$
`# Unity`
