A-Level Maths: D4-07 Arithmetic Sequences: Examples of Finding the Sum of Arithmetic Series

[@femi9000]

Thank you, sir, I appreciate your explanations and help, I'm able to understand due to your evident knowledge in maths.

[@vedaantkothari3560]

Great explaination sir Thank you for the video!

[@augustinelu1446]

May god bless you sir! Thank you so muchhhhhhh for help at math~Amazing videos! You are my life saver!

[@Bad_Siege_Gamer]

Saving the exams of students across the UK🙌

[@dangunning1]

So much better than my teacher

[@Tt05ma]

Hi Jack I was just wondering is it ok to work out L then use first formula instead of using the second formula?

[@Theproofistrivial]

Is it a viable option to find the nth term, then find the last term and use the 1/2n(a+l) formula instead of using the 1/2n[2a+(n-1)d]?

[@TLMaths]

I guess... But I'm unsure why you would if you knew a, n and d and could substitute into the formulae directly.

[@earl8590]

on Q6 why do you plug it in to the bottom equation instead of finding L and plug it into the middle equation

[@TLMaths]

You can do either

[@earl8590]

@@TLMaths cheers man

[@ismailchoudhury]

Do we need to memorize the equations?

[@TLMaths]

You need to memorise the nth term formulae for arithmetic and geometric sequences, but the sum to n terms for arithmetic, the sum to n terms for geometric, and the sum to infinity should all be in the formulae booklet.

[@ismailchoudhury]

@@TLMaths Thanks

[@Doodo981]

TLMaths do you know where we can get a printable sheet of all the equations given to us in the exam

[@TLMaths]

Hi Bradley - which exam board are you doing?

[@Doodo981]

TLMaths edexcel

[@AlEx-ro7kd]

the words to algebra video after this one is not available on your website :(

[@TLMaths]

It's here: sites.google.com/site/tlmaths314/home/a-level-maths-2017/full-a-level/sequences-series/arithmetic-sequences Is there somewhere it's not appearing where you expect it to?

[@TLMaths]

All fixed - thanks for letting me know.

[@lukelehmann4783]

Q3 i think n=107 because it was plus 2 not -2 because (n - 1)x-2 =-2n +2 can someone else check I'm not shore

[@TLMaths]

-116 = 100 + (n-1)*(-2) -116 = 100 - 2n + 2 -218 = -2n 109 = n

[@johom3695]

(267-3)+4=268 not 267

[@TLMaths]

267 = 3 + (n - 1)*4 267 = 3 + 4n - 4 268 = 4n 67 = n Where's the mistake?

[@johom3695]

Wrong for the first one

[@TLMaths]

Don't think so...

[@thedevilbakes3983]

Dude be polite, this legends put up these videos for free to help you. At least explain why you think he’s wrong with some respect ...

[@iiv.dannyboi]

I worked it out and yes its correct. So the difference between the numbers =4 The first number = 3 We need to find n 267= 3+(n-1)×4 264= (n-1)×4 66=n-1 N=66 Im guessing you know how to re-arranged equations. Hope it helped bye

[@emmarosina06]

When he used the second formula he was supposed to say 3x2 since it’s 2a but he only put a 3 that’s why it’s wrong 😊

[@TLMaths]

@@emmarosina06 There are two formulae: S = (1/2)n(a+l) and S = (1/2)n(2a + (n-1)d). I used the first formula: S = (1/2)*67*(3 + 267)