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Help with Math question

GCSEPPBQP.pdf - Google Chrome 04_02_2017 17_13_50.png3 marks
any idea as to how I would solve it?
let n = 1

then let n = 2

think what these numbers mean.
n is the no. of term

To find the first term put n=1
First term is 2
To find the second term
put n=2
Sum of first two terms is 6
But u need the second term instead of the sum of 1st and 2nd therefore subtract
"Sum of first two terms - first term"
Second term is= 6-2=4
Original post by the bear
let n = 1

then let n = 2

think what these numbers mean.


I have considered just subbing in 1 and 2 into the expression, but 1, I thinks its to easy for a 3 mark question and 2, the question states the 'sum of the first n terms' so the expression given isn't the nth term, if you get what I mean?

Its also the last question on the paper
(edited 7 years ago)
Original post by Bloom <3
n is the no. of term

To find the first term put n=1
First term is 2
To find the second term
put n=2
Sum of first two terms is 6
But u need the second term instead of the sum of 1st and 2nd therefore subtract
"Sum of first two terms - first term"
Second term is= 6-2=4


dont give full solutions, its against forum rules
Original post by Bloom <3
n is the no. of term

To find the first term put n=1
First term is 2
To find the second term
put n=2
Sum of first two terms is 6
But u need the second term instead of the sum of 1st and 2nd therefore subtract
"Sum of first two terms - first term"
Second term is= 6-2=4


complete solutions are not welcomed :redface:
Original post by Bloom <3
n is the no. of term

To find the first term put n=1
First term is 2
To find the second term
put n=2
Sum of first two terms is 6
But u need the second term instead of the sum of 1st and 2nd therefore subtract
"Sum of first two terms - first term"
Second term is= 6-2=4


on the 5th line how did you just know the sum of the first two terms is 6 ?
Original post by DylanJ42
dont give full solutions, its against forum rules


Oops i didnt knew that
But why
Here i thought i was helping
Original post by CraigBackner
on the 5th line how did you just know the sum of the first two terms is 6 ?


Because the eq is of sum of n terms
So i put 2 because theres are two terms
Original post by Bloom <3
Because the eq is of sum of n terms
So i put 2 because theres are two terms


ohh i understand now, and thanks for helping!:smile:
Original post by CraigBackner
ohh i understand now, and thanks for helping!:smile:

:smile:
Original post by Bloom <3
Oops i didnt knew that
But why
Here i thought i was helping


generally people will learn better from getting a hint and going on to solve it themselves rather than just reading the full solution. Its okay you didnt know but just in future try to give hints unless the person really really cant do it even after multiple hints
(edited 7 years ago)
Original post by DylanJ42
generally people will learn better from getting a hint and going on to solve it themselves rather than just reading the full solution. Its okay you didnt know but just in future try to give hints unless the person really really cant do it even after multiple hints

Thanks for informing can you tell me where i can find more posts like these to be of some more help to tsr
Original post by Bloom <3
Thanks for informing can you tell me where i can find more posts like these to be of some more help to tsr


do you mean posts regarding forum rules or posts with people needing help?

forum rules are stickied at the top of the forum, https://www.thestudentroom.co.uk/forumdisplay.php?f=38, "posting guide and forum rules - please read"

as for other posts with people needing help, youll mostly find these on the forum page also (some get posted in other forums but theyre usually moved to this forum)
Original post by CraigBackner
GCSEPPBQP.pdf - Google Chrome 04_02_2017 17_13_50.png3 marks
any idea as to how I would solve it?




First step is to make the expression of the sum given to you by the problem in the same format as the last part of the formula above.
Hint 1: Factorise the expression of your sum by 2
Hint 2: Note that (1-r^n)/(1-r) is the same as (r^n-1)/(r-1)
Hint 3: You then find what a and r are, and sub them into the first two expressions in the formula I've given

Edit: Only just realised this is a gcse question and that the sigma I've thrown up there caused confusion (and laughter in some cases :biggrin:).
(edited 7 years ago)

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