Question

Tìm x :

( 1/3 + 1/15 + 1/35 + 1/63 + 1/99 ) x X = 1 

Answer 1

`(1/3+1/15 + 1/35 + 1/63 + 1/99) xx x = 1`

`(2/(1xx3) + 2/(3xx5) + 2/(5xx7) + 2/(7xx9) + 2/(9xx11) xx x = 1`

`(1-1/3+1/3-1/5+........+1/9 - 1/11) xx x =1`

`(1-1/11) xx  x = 1`

`10/11 xx x = 1`

`5/11 xx x = 1`

`x = 1: 5/11`

`x=1 xx 11/5`

`x=11/5`

Answer 2

`(1/(1.3) + 1/(3.5) + ... + 1/(9.11)) xx  x = 1`

`-> (2/(1.3) + 2/(3.5) + ... + 2/(9.11)) xx x  = 2`

`-> (1/1 - 1/3 + 1/3 - 1/5 + ... + 1/9 - 1/11) xx x  = 2`

`-> 10/11 xx x = 2`

`-> x = 2 : 10/11`

`-> x = 11/5`