SOLUTION: Find the formula for the nth term of the geometric sequence with a_2 = -18 and a_5 = 144.

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Question 1087015: Find the formula for the nth term of the geometric sequence with a_2 = -18 and a_5 = 144.
Found 3 solutions by ikleyn, Fombitz, MathTherapy:
Answer by ikleyn(52778) About Me  (Show Source):
You can put this solution on YOUR website!
.
Solved and answered at this link
https://www.algebra.com/algebra/homework/word/geometry/Geometry_Word_Problems.faq.question.1087012.html

https://www.algebra.com/algebra/homework/word/geometry/Geometry_Word_Problems.faq.question.1087012.html


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Ignore the solution by @Fombitz: it is wrong and irrelevant.



Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
a%5Bn%5D=a%5B1%5D%2B%28n-1%29%2Ad
So,
a%5B2%5D=a%5B1%5D%2B%282-1%29%2Ad=-18
1.a%5B1%5D%2Bd=-18
and
a%5B5%5D=a%5B1%5D%2B4d=144
2.a%5B1%5D%2B4d=144
Subtract 1 from 2,
a%5B1%5D%2B4d-a%5B1%5D-d=144-%28-18%29%7D%7D%0D%0A%7B%7B%7B3d=162
d=54
Then from 1,
a%5B1%5D%2B54=-18
a%5B1%5D=-72
So,
a%5Bn%5D=-72%2B%28n-1%2954
a%5Bn%5D=-72%2B54n-54
highlight%28a%5Bn%5D=54n-126%29

Answer by MathTherapy(10551) About Me  (Show Source):
You can put this solution on YOUR website!

Find the formula for the nth term of the geometric sequence with a_2 = -18 and a_5 = 144.
I really wonder, at times, what these people gain by coming into this forum and posting WRONG &/or RIDICULOUS answers to people seeking help with math problems.