Answer:
see explanation
Step-by-step explanation:
(8)
the common ratio r, of a geometric sequence is
r = =
= ......
r = =
= 8
(9)
The simplest way to evaluate the sum is to substitute k = 3, 4, 5, 6 into each term and sum them
(- 9 + 20) + (- 12 + 20) + (- 15 + 20) + (- 18 + 20)
= 11 + 8 + 5 + 2 = 26