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प्रश्न
Find the sum of the first n natural numbers.
उत्तर
The first n natural numbers are 1, 2, 3, 4, 5,……..,n
Here, a = 1 and d = (2 – 1) = 1
Sum of n terms of an AP is given by
`s_n = n/2 [2a +(n-1) d]`
`= (n/2) xx [ 2xx1+(n-1) xx1]`
`= (n/2) xx [ 2+n-1] = (n/2) xx (n+1) = (n(n+1))/2`
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