Question

Find the indicated sum. Show your work.

Answer 1

am i doing it right?

Answer 2

Are you saying that the answer is 0?

Answer 3

i dont think so :/

Answer 4

with summation formula its giving 46 and 2
confuse ...

Answer 5

OK, let's make sure you understand how summation notation works first.

Answer 6

sure :) i have to show my work

Answer 7

Could you tell me what the sum is of this question?
\[\sum_{k=1}^4 2k\]

Answer 8

If not, that is ok, I'll explain... just let me know :)

Answer 9

i guess k= the limit and 4 is upper value

Answer 10

yes please

Answer 11

OK, summation notation is just shorthand... it's a compact way of writing a long addition problem.

Answer 12

In this problem we have the scary looking sigma \[\sum\] which just means "you will add these things together"

Answer 13

hmm

Answer 14

Now, whatever is to the right of the sigma is what the numbers "look like" it is there "shape." This time they look like 2k.. That is 2 multiplied by some number.

Answer 15

But what number should I use? And how many? This is what the "limits" tell us. Start with k = 1... and keep plugging in k's until you reach k = 4.

Answer 16

Of course, I'm still working on the easy problem for now... :)

Answer 17

So, to answer the "easy" problem I gave we would simply do this
\[\sum_{k=1}^4 2k = 2(1) + 2(2) + 2(3) + 2(4)\]

Answer 18

See how the k switches each time? And we just add them together?

Answer 19

ok let me try now

Answer 20

Sure thing!

Answer 21

k will replace numbers from 1-4?

Answer 22

Yes, good

Answer 23

in bracket Ex = (-1)^1(1+11)... etc?

Answer 24

Yes, (-1)^[1] ([1] + 11) + ... and so on.

Answer 25

In this case, there are two k's in the "shape of the number" to replace

Answer 26

after getting all that should i write the sum or different values?

Answer 27

You should first write the whole thing out. And then add the numbers like you would any old day (simplify).

Answer 28

So like \[\sum something = s1 + s2 + s3 + s4 = number\]

Answer 29

ok ill write just give me a min

Answer 30

Go right ahead! :)

Answer 31

=(-1)^1(1+11) +(-1)^2(2+11) +(-1)^3(3+11) +(-1)^4(4+11)

Answer 32

I like what I see so far. :)

Answer 33

(-12)++(13)+(-14)+15

Answer 34

Yep yep, looking nice.

Answer 35

=2

Answer 36

correct?

Answer 37

Good, you are correct. :)

Answer 38

The answer is plain old 2... a lot of work for an easy number huh?

Answer 39

thanks alot :)

Answer 40

yups :P

Answer 41

No worries! You are welcome. Good luck with your studies!

Answer 42

thanks its my last course Excited :)

Answer 43

can i ask others if need to?