SOLUTION: find n for the series for which an =138 a1 =-2 and d=7

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Question 860683: find n for the series for which an =138 a1 =-2 and d=7
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
an = a + (n - 1)d
138 = -2 + 7(n - 1)
138 = -2 + 7n - 7
138 = 7n - 9
147=7n
21=n