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Question
If the first term of an AP is –5 and the common difference is 2, then the sum of the first 6 terms is ______.
Options
0
5
6
15
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Solution
If the first term of an AP is –5 and the common difference is 2, then the sum of the first 6 terms is 0.
Explanation:
Given,
a = –5
And d = 2
∴ S6 = `6/2[2a + (6 - 1)d]` ...`[∵ S_n = n/2[2a + (n - 1)d]]`
= 3[2(–5) + 5(2)]
= 3(–10 + 10)
= 0
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