Mathematics
Find the sum :
9 + 7 + 5 + 3 +……to 14 terms.
AP
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Answer
The above sequence is an A.P. with common difference = 5 - 7 = -2.
We know that,
Sum of n terms of an A.P. is given by,
∴ Sn = [2a + (n - 1)d]
⇒ S14 = [2(9) + (14 - 1)(-2)]
= 7[18 + (13)(-2)]
= 7[18 - 26]
= 7.(-8)
= -56.
Hence, S14 = -56.
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