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.

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.

anonymous · Answer

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

anonymous · Answer

Can you help me solve this?

triciaal · Answer

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

anonymous · Answer

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

anonymous · Answer

i would use a calculator for sure

anonymous · Answer

Ok thank you!

anonymous · Answer

yw