Sorry if the question sounds a bit off, i wasnt quite sure how to word it.
My math question is: given the expression Sn=n^2 + 2n, determine an expression, in simplified form, for Sn-1 in terms of n.
NA (i don't think there are any equations for this)
The Attempt at a Solution
I honestly don't know how to go about this properly but here's what I've done:
First three terms are 3, 8 and 15. All of which have a different 'common ratio' when 8 is divided by 3, its 2.67 but when 15/8 its 1.875?
Which confuses me further, and as for the original question, no idea how to proceed.
Any help is much appreciated, thanks.