Question

Can someone explain summation notation to me?

Answer 1

it is much easier with an example

Answer 2

\[\sum_{k=1}^na_k=a_1+a_2+a_3+...+a_n\] is a start

Answer 3

What do k and n signify?

Answer 4

k= the starting number you put into the general term, n = the last number you'll put into the general term

Answer 5

I thought n was the number of intervals?

Answer 6

so you'll sum up from k to n

Answer 7

nah... i might make a mistake!

Answer 8

?

Answer 9

nope, n = the last number you'll put into the general term

Answer 10

How do you write how many intervals you're taking?

Answer 11

\[\sum_{k=2}^{n=5} n = 2+3+4+5 = 14\]

Answer 12

an example would be best
\[\sum_{_k=1}^5 2k-1=1+3+5+7+9\]

Answer 13

@callisto i think you had a confusion between n and k in your example

Answer 14

k = lower value of interval
n = upper value of interval

Answer 15

not really

Answer 16

sorry.. please correct me!

Answer 17

when you write
\[\sum_{k=1}^5a_k\] k is the index
start at k = 1 and add successive terms until you reach k = 5

Answer 18

\[\sum_{k=2}^{5} k = 2+3+4+5 =14\]correct?

Answer 19

similarly
\[\sum_{k=1}^na_k\] means start at k = 1 and add successive terms until k = n

Answer 20

yes what you wrote second is correct

Answer 21

Successive as in +1 each time?

Answer 22

so
\[\sum_{k=1}^5a_k=a_1+a_2+a_3+...+a_n\]

Answer 23

replace k by 1, then by 2, then by 3 etc
that is if you start at k = 1

Answer 24

next term you might also say +1 of the previous nth term

Answer 25

so the sigma is really just a big fat plus sign

Answer 26

thank you satellite73, you're always a good teacher for me lol

Answer 27

here is another example
\[\sum_{k=1}^5\frac{1}{2^k}=\frac{1}{2}+\frac{1}{2^2}+\frac{1}{2^3}+\frac{1}{2^4}+\frac{1}{2^5}\]

Answer 28

Thanks! That REALLY clears it up for me!

Answer 29

yw