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Maths question help needed

Screen Shot 2016-09-12 at 18.40.12.png
I'm stuck on this series question.. and have no idea how this answer was reached. Please help... :frown: thanks so much!! :biggrin:

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Avatar for Zacken
Zacken
22
Original post by Ipsooo
Screen Shot 2016-09-12 at 18.40.12.png
I'm stuck on this series question.. and have no idea how this answer was reached. Please help... :frown: thanks so much!! :biggrin:

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This is a geometric series, first term xx and common ratio 2x2x. Can you see why?

Now use the formula for the geometric series a(1−rn)1−r\frac{a(1 - r^n)}{1-r} for the sum of the first nn with a=xa = x (first term), r=2xr = 2x (common ratio), n=10n = 10 (first ten terms)
Reply 2
Avatar for Ipsooo
Ipsooo
OP
5
Original post by Zacken
This is a geometric series, first term xx and common ratio 2x2x. Can you see why?

Now use the formula for the geometric series a(1−rn)1−r\frac{a(1 - r^n)}{1-r} for the sum of the first nn with a=xa = x (first term), r=2xr = 2x (common ratio), n=10n = 10 (first ten terms)


Oh dear, I've massively over complicated things... :redface: Thanks sooo much!!
Reply 3
Avatar for Zacken
Zacken
22
Original post by Ipsooo
Oh dear, I've massively over complicated things... :redface: Thanks sooo much!!


No worries. :smile:


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