Question

Write the sum using summation notation, assuming the suggested pattern continues.

5 - 15 + 45 - 135 + ...

HELPPPP

Answer 1

Do those terms look like an arithmetic sequence? Geometric?

Answer 2

geometric

Answer 3

\[\sum_{n=0}^{infinity}5(-3)^n\]
is this the answer?

Answer 4

That was quite a leap. Where did you get that?

Answer 5

Well yes that would be :) I can just edit this a little for you :)
\[\sum^\infty_{n=0}{5(-3)^n}\]

Answer 6

I got that because i know that the lower limit is 0 but im not sure of the index...I do know that the ratio is -3 and the first term is 5

Answer 7

thanks!!!

Answer 8

@KeithAfasCalcLover can you help really fast with another?

Answer 9

Yeah sure!

Answer 10

Write the sum using summation notation, assuming the suggested pattern continues.

64 + 81 + 100 + 121 + ... + n2 + ...
would it be \[\sum_{n=8}^{\infty}n^2\]

Answer 11

Well, good work, then. You seem to have reasoned it out ofter realizing that it was geometric.

Answer 12

thanks :)

Answer 13

The last one looks fine. Neither geometric nor arithmetic.

Answer 14

thank you!

Answer 15

...and you found the \(\infty\) symbol!!

Answer 16

haa YEAH!

Answer 17

By the way,
\[\sum^\infty_{n=0}{5(-3)^n}=\frac{5}{1-(-3)}=\frac{5}{4}\]

Answer 18

huh?

Answer 19

Lol actually I got to go haha so long everybody

Answer 20

so long...

Answer 21

Finding the expression and using the summation notation is your first task. One day, you will be asked to find the sum of expression like these. This is not a really big deal for arithmetic or geometric series. Other series, though, can be a delightful exploration.

Answer 22

i dont understand what keith did

Answer 23

Quite all right. You can add up series later. That is not your assignment for today.

Answer 24

ok. thank you