Answers

  • Brainly User
2016-07-12T15:55:53+08:00
Since it is stated that the given is an arithmetic sequence (a.s), the nth term is:

a₁ = 20        d = (18-20) ⇒ -2

an = a₁ + (n-1)(d)

an = 20 + (n-1) (-2)

an = 20 -2n + 2

an = -2n + 20     ⇒   Rule for the given sequence

To find the 68th term, for example:

a₁ = 20    n = 68   

Use the rule to find the 68th term:

an = -2n + 20

a₆₈ = -2(68) + 20

a₆₈ = -136 + 20

a₆₈ = - 116
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