Question

If the nth term of an a.p ( 2n+1 ) find sum of first n term of the A.P

Answer 1

first term t1 = 2×1 + 1= 3

2nd term t2 = 2×2+1=5

common difference = t2 - t1 =5-3=2

sum of n term = n/2 ( first term + last term)

Sn = n/2 ( 3 + 2n +1)

= n/2 (2n + 4)

= n(n+2)

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