anonymous
  • anonymous
Find S20 for the series -1 + -3 + -5 + -7 +... help?
Mathematics
  • Stacey Warren - Expert brainly.com
Hey! We 've verified this expert answer for you, click below to unlock the details :)
SOLVED
At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga. Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus. Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.
jamiebookeater
  • jamiebookeater
I got my questions answered at brainly.com in under 10 minutes. Go to brainly.com now for free help!
Loser66
  • Loser66
You have formula for this, what is it? Notice: S means sum
anonymous
  • anonymous
s=-1-2n
Loser66
  • Loser66
I don't get. Use draw button to jot it down, please

Looking for something else?

Not the answer you are looking for? Search for more explanations.

More answers

anonymous
  • anonymous
|dw:1439655417621:dw|
Loser66
  • Loser66
https://www.mathsisfun.com/algebra/sequences-sums-arithmetic.html
Loser66
  • Loser66
you need find d. What is d? the difference between 2 consecutive numbers.
Loser66
  • Loser66
|dw:1439655734476:dw|
anonymous
  • anonymous
-2
anonymous
  • anonymous
s20=-39
Loser66
  • Loser66
Your series starts from \(a_1 \) and ends at \(a_{20}\), right? that means you have 20 elements there, right? That is n =20 Now plug all in \(S_{20}= \dfrac{n}{2}(2a_1+(n-1)*d)\) What do you get?
anonymous
  • anonymous
whats a1
anonymous
  • anonymous
i got -420?
Loser66
  • Loser66
a_1 is the first number: -1
anonymous
  • anonymous
-400
Loser66
  • Loser66
yes, hihihi... I am sorry.
anonymous
  • anonymous
-400?
Loser66
  • Loser66
yes
Loser66
  • Loser66
Let's test
Loser66
  • Loser66
hit your calculator -1-3-5.......-39=?
anonymous
  • anonymous
yep
Loser66
  • Loser66
yES, I got -400

Looking for something else?

Not the answer you are looking for? Search for more explanations.