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Please help me on how to do these sums in mathematics, taken from the Chapter- Progressions and Series .
1.) Find sum of the series :
1.n + 2.(n-1) + 3.(n-2) +....+n.1
(Ans is: n(n+1)(n+2)/6 )
2.) If 's' is the sum to infinity of a G.P. whose first term is 'a', then prove that the sum of the first 'n' is :
[1 - (1- a/s)n ]s
3.) Series of natural numbers is divided into groups of :
(1), (2,3,4) , (5,6,7,8,9),......nth group.
Show that the sum of the numbers in the nth group is-
n3 + (n-1)3
Dear student,
This series will be like:
n(1+2+3+................)-2(1+3+5+..................)
Sum of natural numbers=n(n+1)/2
Just use it.....
BEST OF LUCK...............
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