Question

What is the sum of the first nine terms of the geometric series where A1 = 7 and r = -3?

Hint: Sn = a1(1 - r^n)/ 1 - r, where a1 is the first term and r is the common ratio.

Answer 1

plug the numbers in to the formula you are given
that is all

Answer 2

Can you help me solve this?

Answer 3

direct substitution.
write the formula and replace the letters with the values given
compute to simplify

Answer 4

put \(a_1=7\) and \(r=-3\) and compute \[\frac{7(1-(-3)^9)}{1-(-3)}\]

Answer 5

i would use a calculator for sure

Answer 6

Ok thank you!

Answer 7

yw