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Help with sequences and series question

Screen Shot 2016-10-14 at 4.04.25 PM.png
Would really appreciate if someone could help me with this :smile:
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Original post by electrx
Screen Shot 2016-10-14 at 4.04.25 PM.png
Would really appreciate if someone could help me with this :smile:

What have you tried? Post your working.
Original post by electrx
Screen Shot 2016-10-14 at 4.04.25 PM.png
Would really appreciate if someone could help me with this :smile:


So use the formula for the sum of a geometric sequence.

Sn=a(1rn)1r,nN\displaystyle S_n=\frac{a(1-r^n)}{1-r}, n \in \mathbb{N}

You get 2 equations with 2 unknowns and proceed to solve them.

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