Explanation:
In mathematics,
an arithmetic progression (AP) or arithmetic
sequence is a sequence of numbers such that the difference of any two successive members of the
sequence is a constant. For instance, the sequence 3, 5, 7, 9, 11, 13, ... is an
arithmetic progression with common difference 2.
If the initial term of an arithmetic
progression is a_{1} and the common difference of successive members is d,
then the nth term of the sequence is given by:
and in general
A finite portion of an arithmetic progression
is called a finite arithmetic progression and sometimes just
called an arithmetic progression.
http://en.wikipedia.org/wiki/Arithmetic_progression
The
above explanation is copied from Wikipedia, the free encyclopedia and is
remixed as allowed under the Creative Commons Attribution- ShareAlike 3.0 Unported
License.
(Our solved example in mathguru.com uses the below concept. This
is our own explanation, it is not taken from Wikipedia.)
N^{th} term from the end is given
by the formula
N^{th} term from the end = {l -
(n-1) d}
l is the
last term of the AP
n is the
number of terms
d is the
common difference