Question

What is the sum of the geometric sequence 4, 16, 64, … if there are 8 terms?

Answer 1

keep going! do you see the patteren?

Answer 2

Is it just me... or is it an extremely large number?

Answer 3

haha yes it is!

Answer 4

All right, glad I wasn't crazy!

Answer 5

87380

Answer 6

I don't think 87380 is correct. Anyone care to counter?

Answer 7

long way: 4^1+4^2+4^3+4^4+4^5+4^6+4^7+4^8 = 87380


or


short way: 4*(4^8-1)/(4-1) = 87380

Answer 8

either way gets to the same correct answer

Answer 9

i told u it is right!!!!!!!!!!!!!!

Answer 10

Well, I'm wrong... awesome. Good fight guys :P

Answer 11

calculated with my ti nspire color

Answer 12

When you are doing seqences try to generalize the pattern. It will make it very easy for long ones.

for example here you can see it is 4^n where n is the number in the seqence