\(=\dfrac{1}{2}\cdot\dfrac{2}{3}\cdot...\cdot\dfrac{2018}{2019}=\dfrac{1}{2019}\)
`B=(1-(1)/(2))(1-(1)/(3))(1-(1)/(4)).....(1-(1)/(2019))`
`=(2-1)/(2).(3-1)/(3).(4-1)/(4).....(2019-1)/(2019)`
`=(1)/(2).(2)/(3).(3)/(4).....(2018)/(2019)`
`=(1.2.3.....2018)/(2.3.4.....2019)`
`=(1)/(2019)`
B=(1−12)(1−13)(1−14).....(1−12019)B=(1-12)(1-13)(1-14).....(1-12019)
=2−12.3−13.4−14.....2019−12019=2-12.3-13.4-14.....2019-12019
=12.23.34.....20182019=12.23.34.....20182019
=1.2.3.....20182.3.4.....2019=1.2.3.....20182.3.4.....2019
=12019
