Geometric Progression: x, xr, xr^{3}, xr^{4},  are said to be in geometric progression. Here, a is first term and r is common ratio.
a) n^{th} term = xr^{ (n 1)}
b) Sum of n terms = 
x (1 – r^{n}) 
, here r < 1 
(1 – r) 
c) Sum of n terms = 
x (r^{n} – 1) 
, here r > 1 
(r – 1)
