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38 votes
38 votes
Find the 8th term of the geometric sequence 7,−21,63,

User BZezzz
by
3.2k points

2 Answers

14 votes
14 votes

Answer:

a₈ = - 15309

Explanation:

The nth term of a geometric sequence is


a_(n) = a₁
(r)^(n-1)

where a₁ is the first term and r the common ratio

Here a₁ = 7 and r =
(a_(2) )/(a_(1) ) =
(-21)/(7) = - 3 , then

a₈ = 7 ×
(-3)^(7) = 7 × - 2187 = - 15309

User VAr
by
2.5k points
8 votes
8 votes

Answer:

8th term is -15309

Explanation:


{ \boxed{ \bf{u_(n) = a( {r}^(n - 1) ) }}} \\ { \tt{u_(8) = 7( {( - 3)}^(8 - 1)) }} \\ { \tt{u_(8) = 7( - 2187)}} \\ { \tt{u _(8) = - 15309}}

r is the common difference, r = -21/7 = -3

User Elsa Li
by
2.7k points