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Example:Finding nth Term from End.

 Post to:   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 a1 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

(Our solved example in mathguru.com uses the below concept. This is our own explanation, it is not taken from Wikipedia.)

Nth term from the end is given by the formula

Nth 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