Question

The nth term of AP is an=2n+1, find its sum.

Answer 1

Answer:

An =2n+1=a1=2×1+1=3 and a2 =2×2+1=5 so d = a2-a1=5-3=2 so sn = n/2 (2×3+(n-1)2=n/2(6-2n-2)=n/2(4-2n)=n(2-n)=2n-n^2

Step-by-step explanation:

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