SOLUTION: find the sum of the first 16 terms of the arithmetic progression, if the first term is -5 and the common difference is -6 find the first term and common difference for the seque

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Question 694821: find the sum of the first 16 terms of the arithmetic progression, if the first term is -5 and the common difference is -6
find the first term and common difference for the sequence with the given nth term.
an=7.4+0.6n
find the sum: 12+15+18+ . . . +111
a)1887 b)4182 c)369 d)2091

Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
find the sum of the first 16 terms of the arithmetic progression, if the first term is -5 and the common difference is -6
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a(16) -5 +(15)(-6) = -95
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S(n) = (n/2)(a(1)+a(16))
S(16) = 8(-5-95) = 8(-100) = -800
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find the first term and common difference for the sequence with the given nth term.
an=7.4+0.6n
a(1) = 7.4+0.6 = 8
a(2) = 7.4+0.6*2 = 7.4 = 1.2 = 8.6
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Common difference = 0.6
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find the sum: 12+15+18+ . . . +111
a(1) = 12 ; d = 3
Find "n" using 111 = 12 + (n-1)3
99 = (n-1)3
n-1 = 33
n = 34
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Sum = (34/2)(12+111) = 17*123 = 2091
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Cheers,
Stan H.
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a)1887 b)4182 c)369 d)2091