Question

Find the sum of the infinite series 4 + 3.2 + 2.56 + 2.048 +...if it exists.

Answer 1

@Loser66 can u help?

Answer 2

i cant remeber what the formula for sum is

Answer 3

Sn=a1*1-n/1-n i think?

Answer 4

this is a geometric series

sum to infinity = 1 / (1 - r)

where a = frist term and r = common difference

Answer 5

sorry that' s a / (1 - r)

Answer 6

to find r divide 2nd term by first
this should equal 3rd / 2nd

Answer 7

4/(r-.8)

Answer 8

4/(1-.8)

Answer 9

yes

Answer 10

i got .05

Answer 11

you ve gone wrong somewhere

= 4 / (1 - 0.8) = 4 / 0.2

Answer 12

20

Answer 13

thats it

Answer 14

how would i know if it doesnt exists?

Answer 15

here each term is decreasing - so the sum converges to a certain value

If each term was greater than the last the sum would diverge - a limit would not exist

Answer 16

okay.
can u help me with a few more please? im still trying to get the hang out this

Answer 17

eg 2 + 4 + 6 diverges

Answer 18

ok

Answer 19

should i ask here or open a new post

Answer 20

best to open a new post