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Sequences and Series Question (1 Viewer)

phoenix159

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Joined
May 19, 2013
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79
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Male
HSC
2014
Find the sum of the first n terms of Tr = 2r + 2r - 1 (its the sum of an arithmetic and geometric series)

I got n2 - n/2 + 2n+1 - 2

But the textbook says n2 + 2n+1 - 2
 

bottleofyarn

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Joined
Sep 22, 2013
Messages
50
Gender
Male
HSC
2013
Find the sum of the first n terms of Tr = 2r + 2r - 1 (its the sum of an arithmetic and geometric series)

I got n2 - n/2 + 2n+1 - 2

But the textbook says n2 + 2n+1 - 2
It looks like you've got the geometric sum down pat (2n+1 - 2) So then it's just a matter of the arithmetic sum and -1s. My guess is that you missed the multiplication by 2 since
.
Stuff cancels out and it should give you the answer.
 

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