find the sum of first 15 terms of the following ap
i)11,6,1,-4,-9
ii) 7,12,17,22,27
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find the sum of first 15 terms of the following ap
i)11,6,1,-4,-9
ii) 7,12,17,22,27
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Answer:
(1)360
Step-by-step explanation:
(1) a=11, d=-5, n=15
Sn=n/2(2a+(n-1)d)
=15/2[2(11)+(15-1)-5
=15/2[22+14(-5)]
=15/2(22-70)
=15/2(48)
=15(24)
=360