`M = \frac{1}{3} + \frac{1}{15} + \frac{1}{35} + \frac{1}{63} +...+ \frac{1}{1599}`
`M = \frac{1}{1.3} + \frac{1}{1.5} + \frac{1}{5.7} + \frac{1}{7.9} +...+ \frac{1}{39.41}`
`M = \frac{1}{2} \times (1 - \frac{1}{3} + \frac{1}{3} - \frac{1}{5} + \frac{1}{5} - \frac{1}{7} + \frac{1}{7} - \frac{1}{9} +...+ \frac{1}{39} - \frac{1}{41})`
`M = \frac{1}{2} \times (1 - \frac{1}{41})`
`M = \frac{1}{2} \times \frac{40}{41}`
`M = \frac{20}{41}`
`\text{Vote hay nhất nhé!}`
