+ ... +
Prove using induction, that the above is equal to
Base case:
S(1) = 5
and
Hypothesis:
Assume
(*)
holds for n=k.
Now let n=k+1:
Re-writing the S(k) term using (*):
+
Now re-arrange (step-by-step shown):
add and subtract
finally:
Thus (*) is true for n=k+1