Question

rewrite the following sequence so that it represent a series rather than a sequence
3,9,27,81

Answer 1

Do you see the trend that is occurring?

Answer 2

yes they are mutiplying by 3

Answer 3

So you start with k=1 where 3^1=3
Then, you have 3^2, which is 3*3 or 9
then 3^3 or 3*3*3 or 27
The exponent is increasing by 1 each time.
\[\sum_{k=1}^{4} 3^k\]

Answer 4

do i need to write more to it

Answer 5

nope. That's it.

Answer 6

For more read-up: http://www.purplemath.com/modules/series.htm

Answer 7

thank you so much

Answer 8

can you help me with one more question @Grazes

Answer 9

mhmm

Answer 10

find the sum of the geometric sequence 2,4,8,... if there are 20 terms

Answer 11

@Grazes

Answer 12

so you want the k to start from 1 and end at 20.
the trend is 2^x
\[\sum_{k=1}^{20}2^k\]

Answer 13

thank you