Question

01 Find the sum of first n terms of an AP whose nth term is 1 - 4n.

Answer 1

Answer:

$s = - n(1 + 2n)$

Explanation:

$nth \: term = 1 - 4n \\ for \: first \: term \: put \: n = 1 \\ a |1| = 1 - 4 = - 3 \\ a |2| = 1 - 8 = - 7 \\ \: since \: \\ sum = \frac{n}{2} (first \: term \: + nth \: or \: last \: term) \\ s = \frac{n}{2} ( - 3 + 1 - 4n) \\ s = - n(1 + 2n)$

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