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The first term of an arithmetic sequence is −12 . The common difference of the sequence is 7. What is the sum of the first 30 terms of the sequence?

 Jan 23, 2020
 #1
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 Jan 23, 2020
 #2
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Let  t1 = first term                   --->     t1  =  -12

Let d = common difference     --->     d  =  7

Let n = number of terms         --->     n  =  30

Let t n = nth term                     --->     tn  =  t1 + (n - 1)·d     --->     t30  =  -12 + (30 - 1)·7     --->     t30  =  191

Let S = sum of the terms        --->     S  =  n(t1 + tn)/2     --->     S  =  30(-12 + 191)/2     --->     S  =  your answer

 Jan 23, 2020

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