b1•(q^n–1) 224•(q^n–1)
Sn = --------------- = ------------------ =
q–1 -0,5
= –448•(q^n–1)
–448•q^n+448 = 441
–448•q^n = –7
q^n = 1/64
(1/2)^n = (1/2)^6
n=6
(7/8-1/4)·2/5=0,25
1) 7/8-1/4=(приводим к общему знаменателю 8)=5/8
2) 5/8 · 2/5=(сокращаем 5 и 5)=2/8=1/4=0,25