Question

Find the sum of the n terms of the following series.
$(1) + (1 + 2) + (1 + 2 + 3) + .......$
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Answer 1

Sn = n/2 {2a + (n-1)d}

Here the series will be formed as 1,3,5,7..... nth term

a = 1, An = n, d = 2

Sn = n/2 {2 + (n-1)2}

Sn = n/2 {2 + 2n - 2}

Sn = n/2 {2n}

Sn = n {n}

Sn = n^2

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