Write an expression for Sn

teraslintu

New member
Joined
Sep 21, 2019
Messages
1
a) Write an expression for Sn, for the series 1 + 7 + 13 + ...

b) Hence, find the value of n for which Sn=833

Please help me.... I don't even know where to begin
 
a) Write an expression for Sn, for the series 1 + 7 + 13 + ...
Each term is the series is an=1+6(n1)=6n5\displaystyle a_n=1+6\cdot(n-1)=6n-5
Sn=k=1n(6k5)= ?\displaystyle {S_n} = \sum\limits_{k = 1}^n {(6k - 5)}=~?
 
Each term is the series is an=1+6(n1)=6n5\displaystyle a_n=1+6\cdot(n-1)=6n-5
Sn=k=1n(6k5)= ?\displaystyle {S_n} = \sum\limits_{k = 1}^n {(6k - 5)}=~?

I've deleted my post since this one makes it obsolete.
 
Top