`1)`
`(1 - 1/2) xx (1 - 1/3) xx (1 - 1/4) xx ... xx (1 - 1/100) + x/100 = 16/15 xx (1/2 + 1/4 + 1/8 + 1/16)`
`⇒ 1/2 xx 2/3 xx 3/4 xx ... xx 99/100 + x/100 = 16/15 xx [ (1 - 1/2) + (1/2 - 1/4) + (1/4 - 1/8) + (1/8 - 1/16) ]`
`⇒ (1 xx 2 xx 3 xx ... xx 99) / (2 xx 3 xx 4 xx ... xx 100) + x/100 = 16/15 xx (1 + 1/2 + 1/2 - 1/4 + 1/4 - 1/8 + 1/8 - 1/16)`
`⇒ 1/100 + x/100 = 16/15 xx (1 - 1/16)`
`⇒ (x + 1)/100 = 16/15 xx 15/16`
`⇒ (x + 1)/100 = 1 = 100/100`
`⇒ x + 1 = 100`
`⇒ x = 100 - 1 = 99`
`Vậy x = 99`
`2)`
`(1 - 1/2) xx (1 - 1/3) xx ... xx (1 - 1/2014) xx (1 - 1/2015) xx a = 1`
`⇒ 1/2 xx 2/3 xx ... xx 2013/2014 xx 2014/2015 xx a = 1`
`⇒ (1 xx 2 xx ... xx 2013 xx 2014) / (2 xx 3 xx ... xx 2014 xx 2015) xx a = 1`
`⇒ 1/2015 xx a = 1`
`⇒ a = 1 : 1/2015`
`⇒ a = 2015`
`Vậy a = 2015`
