Question

Find the sum of a finite geometric sequence from n = 1 to n = 6, using the expression −2(5)^(n − 1).

Answer 1

@Nnesha

Answer 2

I know you're supposed to use Sn= a1 - an(r) / 1-r, and I had a1=-2 and an (or a6) = -6250. But when I tried to solve I didnt get any of my multiple choice answers.

Answer 3

formula is \[\huge\rm s_n = \frac{ a_1(1-r^n )}{ 1-r }\]
where r is common ratio
n is number of terms

Answer 4

Oh I must've gotten the wrong formula :(
So r is 5 and n is 6, right?

Answer 5

yep

Answer 6

Oh I got it now. Thank you! :)

Answer 7

np :-)