Question
Find the sum to n terms of the AP:
5, 2, -1, -4, -7, ...
5, 2, -1, -4, -7, ...
Answer: Option A
:
A
The given sequence is5, 2, -1, -4, -7, ...., an APwith first term a=5 and common difference d=2−5=−3.
The sum to n terms of an AP of first term a and common difference d is
Sn=n2[2a+(n−1)d].⇒Sn=n2[10+(n−1)(−3)]
=n2[10−3n+3]
=n2[13−3n]
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:
A
The given sequence is5, 2, -1, -4, -7, ...., an APwith first term a=5 and common difference d=2−5=−3.
The sum to n terms of an AP of first term a and common difference d is
Sn=n2[2a+(n−1)d].⇒Sn=n2[10+(n−1)(−3)]
=n2[10−3n+3]
=n2[13−3n]
Was this answer helpful ?
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