Question

The first and second terms of an exponential sequence (GP) are respectively the first and third terms of a linear sequence (AP) . The fourth term of the linear sequence is 10 and the sum of it's first five terms is 60. Find the first five terms of the linear sequence and the sum of the first n terms

Answer 1

ar = a+2d -- but who cares?
a+3d = 10
5/2 (2a+4d) = 60

16,14,12,...

the GP has nothing to do with the AP.

Sn = n/2 (32+(n-1)(-2)) = 17n - n^2

Answer 2

I don't understand this question
Can you show the full wokings