SOLUTION: If an= 27 , a1= -12 and d=3 find n

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Question 1154461: If an= 27 , a1= -12 and d=3 find n
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
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If an= 27 , a1= -12 and d=3 find n
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A%5Bn%5D=A%5B1%5D%2Bd%28n-1%29


You are given system%28A%5B1%5D=-12%2Cd=3%2CA%5Bn%5D=27%29.
Just substitute and solve.

Answer by ikleyn(52794) About Me  (Show Source):
You can put this solution on YOUR website!
.

In arithmetic progression


    a%5Bn%5D = a%5B1%5D + (n-1)*d.


In your case, it takes the form


    27 = -12 + (n-1)*3.


From this equation


    n-1 = %2827%2B12%29%2F3 = 39%2F3 = 13.


Hence,  n = 13 + 1 = 14.    ANSWER

Solved.

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For introductory lessons on arithmetic progressions see
    - Arithmetic progressions
    - The proofs of the formulas for arithmetic progressions
    - Problems on arithmetic progressions
    - Word problems on arithmetic progressions
in this site.

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

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