Geometric Progressions

Question 1

GP Un equation

Answer 1

Un = ar^(n - 1)

Question 2

GP Sn equation

Answer 2

Sn = a(r^(n - 1)) / (r - 1)      (+ve)
Sn = a(1 - r^n) / (1 - r)      (-ve)

Question 3

GP S∞ equation

Answer 3

if I r I < 1

S∞ = a / (1 - r)