anybody?

anugaman · Oct 9, 2009 3:12 PM

For arithmetic sequence, we have two basic formulas S = ( n / 2 ) ( A + T ) wherein S = sum of n terms n = number of terms A = first term T = last term If the last term is not given instead only the first term is given we use the formula that visibleman_7887 has mentioned S = ( n / 2 ) [ 2A + ( n - 1 ) * d ] wherein S = Sum of n terms n = number of terms A = first term d = common difference Source: http://answers.yahoo.com/quest...

NightElf · Oct 9, 2009 3:59 PM

i dunt know how to start. formula only doesnt help.anybody

anugaman · Oct 9, 2009 9:57 PM

To give u a hint,  the first 100th sum consists of only two terms N2 and N99 since all the other terms cancel out. There is a very easy method to calculate it. The only terms involved in the final calculation depend upon N1 and N2 only. It's not even necessary to calculate N99.   If it's not a physics problem but a numerical analysis problem then you can solve it by writing a simple script using either iteration or recursion. It would be similar to solving a Fibonacci Series. -Cowboy Last edited: 09-Oct-09 10:25 PM

cowboy · Oct 9, 2009 10:19 PM

Another hint. The final solution is: 2*N2 - N1. I would like you to figure out how it's derived tho. Regular summation formulas can't be used since the sequence is not monotonous.

cowboy · Oct 10, 2009 7:48 PM