Maths - Geometric sequences C2. Question 8 mixed exercise

Hello,

A sequence of numbers U1, U2...Un is given by the formula Un = 3(2/3)^n - 1

Find the values of u1 u2 and u3

Which I did.

When i cam to the second part I thought that to find the common ratio I do it by the usual method of dividing u1/u2 which is wrong obviously...

I just found it a bit tricky to do because that seems like the thing you would do - does anyone understand what I mean?

The common ratio is 2/3 - I suppose I am just frustrated that that just didnt come to mind as I was reading it and trying to do part b which asks

show that the sum of the first u1 - u15 = -9.014

Anyway explain it better to me than the book is??

Thanks

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