What is the difference between arithmetic progression and geometric progression?
In an arithmetic progression the difference between each term
(except the first) and the one before is a constant. In a geometric
progression, their ratio is a constant. That is, Arithmetic
progression U(n) - U(n-1) = d, where d, the common difference, is a
constant and n = 2, 3, 4, ... Equivalently, U(n) = U(n-1) + d =
U(1) + (n-1)*d Geometric progression U(n) / U(n-1) = r, where r,
the common ratio is a non-zero constant and n = 2, 3, 4, ...
Equivalently, U(n) = U(n-1)*r = U(1)*r^(n-1).