Given the first four terms and the number of terms of the geometric series,find the finite sum. -2-6-18-54-...,n=9

Question

a.)-11,682 b.)-21,682 c.)-19,682 d.)-19,569 help URGENT!!!!

Answer 1

S_n = a₁ (1 - rⁿ) / (1 - r), where a₁ = first term, n = number of terms, r = common ratio.

 

S₉ = (-2)(1 - (3)⁹) / (1 - 3)

S₉ = (-2)(1 - 19683) / -2

S₉ =1 - 19683

S₉ = -19682