Answers

  • Brainly User
2016-06-25T20:22:09+08:00
3 = 9/3

Find the common difference:
a₂ - a₁ = 7/3 - 9/3  = -2/3
a₃ - a₁ = 5/3 - 7/3  = -2/3

d = -2/3        a₁ = 3        an = -27        n = ?

General formula:
an = a₁ + (n-1)(d)

-27 = 3 + (n-1)(-2/3)
-27 = 3 -  \frac{2}{3} n +  \frac{2}{3}

Multiply each term by LCD 3:

3 [-27 = 3 -  \frac{2}{3}n  \frac{2}{3} ]3

-81 = 9 -2n + 2

-81 = 9 + 2 - 2n

-81 = 11 - 2n

2n = 11 + 81

2n = 92

2n/2 = 92/2

n = 46

ANSWER:  -27 is the 46th term of the series.
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