SOLUTION: 1.[A]the 18th term of an arithmetic progression is 25.find it 1st term if is common is 2? [b1]find the common ratio[b2]the 8th term [b3]nth term of the geometric progression

Algebra ->  Sequences-and-series -> SOLUTION: 1.[A]the 18th term of an arithmetic progression is 25.find it 1st term if is common is 2? [b1]find the common ratio[b2]the 8th term [b3]nth term of the geometric progression       Log On


   

Question 102758: 1.[A]the 18th term of an arithmetic progression is 25.find it 1st term if is common is 2? [b1]find the common ratio[b2]the 8th term [b3]nth term of the geometric progression
Answer by stanbon(75887) About Me  (Show Source):
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1.[A]the 18th term of an arithmetic progression is 25.find it 1st term if is common is 2? [b1]find the common ratio[b2]the 8th term [b3]nth term of the geometric progression
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Comment: I'm not sure I understand your question.
#1. You have an arithmetic progression where a(18)=25 ; you want to find
the 1st term if the common difference is 2. If that is the question,
a(18) = a(1)+17d
25 = a(1) + 34
a(1) = -9
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#2. Now you are talking about a geometric progression and you want to
find the ratio of the 8th term to the nth term. If that is the question
a(8)/a(n) = [1-r^9] /[1-r^(n+1)]
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Cheers,
Stan H.