Question

1.) What is the 10th term of the geometric sequence 400, 200, 100…?
A. 0.09765625
B. 0.390625
C. 0.78125
D. 1.5625

2.) what is the sum of the series?


A. -220
B. -110
C. -95
D. 110

Answer 1

\[\sum_{n-1}^{20} (5-n)\]

Answer 2

you see the common ratio which is r is 0.5 in the first question :3 so use the formula ar^(n-1)

Answer 3

its C :D

Answer 4

a=400 r=0.5 n=10 :3 so u get 0.78

Answer 5

so you plug in 400 ,200 and 100?

Answer 6

nooo. r is the common ratio so if u multiply 400 by 0.5 u get 200 and multiply that by 0.5 u get 100 so that means R=0.5 and A is the first term which is 400. so plug these values in a

Answer 7

and find the value of the 10th term :3

Answer 8

thank you so much could you help me with # 2

Answer 9

okie wait :3

Answer 10

okie look in Sigma notation u have to go from the value given at the bottom to the value given at the top.

Answer 11

the answer will be in negative most probably :3

Answer 12

start from 5-1-1 then 5-2-1 then 5-3-1 then keep going till u reach twenty add them all and you'll get the answer :3 i hope it helps ^^
Dont forget to fan and medal :3!