If the nth term of an AP is (2n+1).find the sum of firstn terms of the

1.	If the nth term of an AP is (2n+1).find the sum of firstn terms of the AP
Answer» Let, first term is A1=2×1+1 =3 Second term A2=2×3+1 =7Now, D=A2 - A1 D=7 - 3 D= 4Then, sum of first (n) terms Sn = n/2[2a+(n-1)d]Sn =n/2[2×3+(n-1)4]Sn=n/2[6+4n-4]Sn=n/2[2+4n]Sn=n ^2+n [Hence, Sn=n square +n]

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