if S 1 7 3 7 2 7 7 3 13 7 4 then S 1 25 111 2 25

S= 1/7 + 3/(7^2) + 7/(7^3) + 13/(7^4)+21/7^5 ....
s-s/7=1/7 + 2/(7^2) + 4/(7^3) + 6/(7^4)+8/7^5 ....=6s/7
6s/7-s/7=1/7 + 1/(7^2) + 2/(7^3) + 2/(7^4)+ ....
5s/7=8/49+(2/243)/(1-1/7)(infinite series formula)
5s/7=8/49+2/49=10/49
s=2/7 ans......
none of these
10 years agoHelpfull: Yes(3) No(0)
S= 1/7 + 3/(7^2) + 7/(7^3) + 13/(7^4)+ ........ eq 1
s-1/7 = 3/(7^2) + 7/(7^3) + 13/(7^4)+ ........
7s-1 = 3/7 + 7/(7^2) + 13/(7^3)+ ........ eq2
eq2-eq1:
6s-1 = 2/7+4/(7^2)+6/(7^3)+8/(7^4)+........
3s-1/2= 1/7 + 2/(7^2)+3/(7^3)+4/(7^4)+........ Eq3
3s-1/2-1/7 = 2/(7^2)+3/(7^3)+4/(7^4)+........
21s-9/2 = 2/(7)+3/(7^2)+4/(7^3)+........ Eq4
Eq4-Eq3
18s-4 = (1/7)/(1-1/7)
18s -4 = 1/6
18s = 1/6 + 4
18s = 25/4
s = 25/108

so ans is option B
9 years agoHelpfull: Yes(3) No(0)
S= 1/7 + 3/(7^2) + 7/(7^3) + 13/(7^4)+21/7^5 ....
s-s/7=1/7 + 2/(7^2) + 4/(7^3) + 6/(7^4)+8/7^5 ....=6s/7
6s/7-6s/49=1/7 + 1/(7^2) + 2/(7^3) + 2/(7^4)+ ....
36s/49=8/49+(2/243)/(1-1/7)(infinite series formula)
36s/49=8/49+2/49*6=50/49*6
s=50/216
s=25/108
option 2 is right ans .........
s=2/7 ans......
none of these
10 years agoHelpfull: Yes(0) No(0)

if S= 1/7 + 3/(7^2) + 7/(7^3) + 13/(7^4)+ ........ then S =

1)25/111
2)25/108
3)25/216
4)1/4