Need Help!!! Summation problem

[dosco]

Hello!

I am new to excel and still trying to figure out the formulas. I am working on a summation problem and was wondering if this could be done in excel.

X = A *(B)^n where n starts from 0 to 39.

So basically A multiplied by Summation of B raise to the power of n where n goes from 0 to 39.

Thanks,
Dosco

[shg]

Welcome to the board.

=a * (b^(n+1) - 1) / (b-1)

[Crooza]

Try this as a array formula (cntrl + Shft + enter) to get the sqiggly brackets {}

=SUM(B1^(ROW(1:39)))*A1+ A1

where A1 = A and B1 = B


Edit Added an A1 to teh end of the formula to account for A * B^0

[MarvinP]

Hi dosco and welcome to the forum,

shg is a lot smarter than I am and most likely knows what you are getting at, but look at how I interpret your problem.

[dosco]

You guys are the best...

Thank you all

Dosco