if nth term of an AP is (2n+1) find the sum of first n terms of AP

1.	if nth term of an AP is (2n+1) find the sum of first n terms of AP
Answer» Here, an = 2n + 1Put n = 1, 2. Then,a1 = 2(1) + 1 = 3{tex}\\therefore {/tex}\xa0a2 = 2(2) + 1 = 5a = 3d = a2 - a1 = 5 - 3 = 2{tex}\\therefore {/tex}\xa0Sum of first n-terms of the AP = Sn{tex} = \\frac{n}{2}\\left[ {2a + (n - 1)d} \\right]{/tex}{tex} = \\frac{n}{2}\\left[ {2(3) + (n - 1)2} \\right]{/tex}= n (3 + n - 1)= n (n + 2)

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