What is the sum of the geometric sequence -3 18 -108.... If there are 8 terms? Precalculus 1 Answer G_Dub Apr 7, 2018 #S_8=719835# Explanation: To find the sum of the first #S_n# terms of a geometric sequence, use the formula #S_n=(a(1-r^n))/(1-r)# where #n# is the number of terms #a# is the first term and #r# is the common ratio. #a=-3, r=-6 and n=8# #S_8=((-3)(1-(-6)^8))/(1-(-6))# #S_8=((-3)(1-1679616))/(7)# #S_8=((-3)(-1679615))/(7)# #S_8=719835# Answer link Related questions How do I determine the molecular shape of a molecule? What is the lewis structure for co2? What is the lewis structure for hcn? How is vsepr used to classify molecules? What are the units used for the ideal gas law? How does Charle's law relate to breathing? What is the ideal gas law constant? How do you calculate the ideal gas law constant? How do you find density in the ideal gas law? Does ideal gas law apply to liquids? Impact of this question 6085 views around the world You can reuse this answer Creative Commons License