Answers

2016-07-26T20:10:58+08:00
2016-07-26T20:49:28+08:00
Solution: an=a1 + (n-1)d a18=a1 + (18-1)d 87=2 +18d-1d 87=2 +17d 87-2=17d 85=17d 85/17=17d/17 5=d d=5,5 is the common difference.
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