SOLUTION: the 18th and 52nd terms of an arithmetic progression are 3 and 173 respectively. find 25th term

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Question 393555: the 18th and 52nd terms of an arithmetic progression are 3 and 173 respectively. find 25th term
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
a18 = a1 + 17d = 3
a52 = a1 + 51d = 173.
Subtracting the top equation from the bottom equation, we get 34d = 170
==> d = 5. ==> a1 = -82, by substituting d= 5 into the top equation.
==> a25 = -82 + 24*5 = 38.