SOLUTION: Find a 1 when d equals=−3 and a 9=3. a 1= I really don't want to screw this problem up as when I do these problems I am usually off by a couple of whole numbers I need an e

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Question 1103120: Find a 1 when d equals=−3 and a 9=3.
a 1=
I really don't want to screw this problem up as when I do these problems I am usually off by a couple of whole numbers I need an exact correct answer please so I don't get the wrong answer.
Answer by ikleyn(52788)   (Show Source): You can put this solution on YOUR website!
.
You, probably, talk about an arithmetic progression and  = 3 is its 9-th term.


For n-th term of an arithmetic progression, the general formula is


 = .


In your case   =  = ,


which implies   =  = 3 + 24 = 27.


Answer.   = 27.


Check.   n:     1    2    3    4    5    6    7    8    9
 
         :   27   24   21   18  15    12   9    6    3     ! Correct !

-------------------
There is a bunch of introductory lessons on arithmetic progressions in this site:
    - Arithmetic progressions
    - The proofs of the formulas for arithmetic progressions
    - Problems on arithmetic progressions
    - Word problems on arithmetic progressions


Also,  you have this free of charge online textbook in ALGEBRA-II in this site
    - ALGEBRA-II - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Arithmetic progressions".


Save the link to this textbook together with its description

Free of charge online textbook in ALGEBRA-II
https://www.algebra.com/algebra/homework/complex/ALGEBRA-II-YOUR-ONLINE-TEXTBOOK.lesson

into your archive and use when it is needed.



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