Wed December 07, 2011 By:

n(n-1)(n-2).......(n-r+1) how do we get (n-r+1)?explain with an numerical example

Expert Reply
Thu December 08, 2011
The given product is n(n-1)(n-2) and so on..
Which can be written as (n-0)(n-1)(n-2) ..and so on..
In the above product,the first term is (n-0).
The second term is (n-1),the third term is (n-2) and so on...
So,if we take the no of the term to be 'r'.
For the first term ,r=1,keeping 'n' as fixed.
We can write the First term=(n-0) as (n-1+1)
Similarly,second term=(n-1) can be written as:
Third term=(n-2),can be written as (n-3+1)
Generalising and Proceeding similarly,
we get the rth term as (n-r+1)
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