Sn = a1(1-q n)/(1-q)
Ak = lim (n-> ∞) (Sn -Sk)
= lim (n->; ∞) a1(q k-q n)/(1-q)
N=2
A2 = lim (n-> ∞) a1(q 2-q n)/(1-q)
= a1lim (n-> ∞) (q 2-q n)/(1-q)
A1q = a1lim (n-> ∞) (q 2-q n)/(1-q)
Q-q 2 = 숲 (n-> ∞) (q 2-q n)
Q-q 2 = q 2
Q(2q- 1)=0
Q= 1/2