SOLUTION: Given a1=3, and a5=-17 (the first and the fifth number in an arithmetic series) what's a20 (the twentieth term in the series)

Algebra ->  Sequences-and-series -> SOLUTION: Given a1=3, and a5=-17 (the first and the fifth number in an arithmetic series) what's a20 (the twentieth term in the series)      Log On


   

Question 1197683: Given a1=3, and a5=-17 (the first and the fifth number in an arithmetic series) what's a20 (the twentieth term in the series)
Found 2 solutions by ewatrrr, MathTherapy:
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!

Hi 
arithmetic series:  a1=3, and a5=-17
 a%5Bn%5D=a%5B1%5D%2B%28n-1%29%2Ad   | Need to Know
 a%5B5%5D=3+%2B%284%29%2Ad+=+-17  d = -5
 a%5B20%5D=3%2B%2819%29%28-5%29
    a20 = -92

Wish You the Best in your Studies.


Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!
Given a1=3, and a5=-17 (the first and the fifth number in an arithmetic series) what's a20 (the twentieth term in the series)
Common difference, or 
                        

                    matrix%281%2C3%2C+a%5Bn%5D%2C+%22=%22%2C+a%5B1%5D+%2B+%28n+-+1%29d%29 ------ Formula for a specific term of an AP
                   matrix%281%2C3%2C+a%5B20%5D%2C+%22=%22%2C+3+%2B+%2820+-+1%29-+5%29 ----- Substituting 20 for n, 3 for a1, and - 5 for d
AP's 20th term, or