Geometric Progression
A geometric progression (also known as a geometric sequence or a geometric series) is a sequence of numbers where each term after the first is found by multiplying the previous term by a fixed number called the common ratio. Example: 1,3,9,27... common ratio is 3.
Also a, b, c, d, ... are said to be in Geometric Progression (GP) if b/a = c/b = d/c etc.
1.A GP is of the form 
etc.
Where a is the first term and r is the common ratio.
2.The nth term of a Geometric Progression is given by
.
3.The sum of the first n terms of a Geometric Progression is given by
1.When r<1
2.When r>1 
3.When r =1 the progression is constant of the for a,a,a,a,a,...etc.
4.Sum of the infinite series of a Geometric Progression when |r|<1 is:
5.Geometric Mean (GM) of two numbers a and b is given by 
.
