Answers

  • Brainly User
2016-07-08T08:56:18+08:00
General formula: an = a₁ + (n-1 (d)

an = 87     n = 18      a₁ = 2

87 = 2 + (18-1) (d)
87 = 2 + 17d
17d = 87-2
17d = 85
17d/17 = 85/17
d = 5

ANSWER:
Common difference = 5
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