(1\(3+根号3))+(1\(5根号3+3根号5))+(1\(7根号5+5根号7))+…………+1\(49根号47+4

(1/(3+根号3)) = (1/(1*3*2))*(3-根号3)
(1/(5根号3+3根号5)) = (1/(3*5*2))*(5根号3-3根号5)
(1/(7根号5+5根号7)) = (1/(5*7*2))*(7根号5-5根号7)
…………
(1/(49根号47+47根号49)) = (1/(47*49*2))*(49根号47-47根号49)
右边式子展开相加 前后项会消掉 只留下第一项和最后一项
所以答案为 3/7