Page 21 - Math SL HB Sem 1

GEOMETRIC SEQUENCB

Definition: A sequence

1\ U
, 2,117,. -. > u a,.- - t
is called a geometric
sequence ( or progression
), ifthere exists
a nonzero constant r, called a common ratio, such that
un
=r forn> I
ll,
t

In general ila Gp has a first term
%, and a corrunon ratio r, the geometric sequence is
ut, t\t, utr2,..., rrrn-,
JJJ
First term third
nth term

term
The n', term is u, - ,,rn-t

Example l: Find the n
term and the 8 tcrm for
-l 9
8l ,..

2-9