A community for students.
Here's the question you clicked on:
 0 viewing
anonymous
 one year ago
Find s10 for 1+7+13+19+...
anonymous
 one year ago
Find s10 for 1+7+13+19+...

This Question is Closed

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.1what pattern do you notice in this sequence?

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.1not, exactly. You go down by 6 every time (i.e. subtract 6) BUT the correct notation is d=6

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.1when you say d=6 that would mean you subtract 6, if you say r=6 that would mean you are multiplying times 6 d = common difference (adding) r = common ratio (multiplying)

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.1You need to find the 10th term first, can you do that for me?

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.1[[ Use \(\large a_{\rm n}=a_1+{\rm d( n}1) \) ]]

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.1Oh, a(10)=1+(6)(101)=1+(6)(9)=154=55 correct \(a_{10}=55\)

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.1Now, (when you start from \(a_1\) and end the series at \(a_n\) (provided this series is arithmetic, which it is in this case) the sum, for n terms is given the following way: \(\large\color{black}{ \displaystyle \sum_{ {\rm n}=1 }^{ {\rm n} } A_{\rm n}=\color{red}{\frac{1}{2} \left(a_1+a_{\rm n}\right)}\times \color{blue}{{\rm n}} }\)

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.1in red I labeled the part of the formula which is the average term. in blue is the number of term

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.1number of terms*

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.1well, I should have made the number of terms k... but I will show you how to use this. \(\large\color{black}{ \displaystyle \sum_{ {\rm n}=1 }^{ {\rm 10} } A_{\rm n}=\color{red}{\frac{1}{2} \left(1+55\right)}\times \color{blue}{{\rm 10}} }\)

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.1in this case.... c y?

SolomonZelman
 one year ago
Best ResponseYou've already chosen the best response.1(if you want I can restart in a more handy way, typing isn't a problem.... )

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0I got 280 is that right? @SolomonZelman
Ask your own question
Sign UpFind more explanations on OpenStudy
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.