Combining Partial Sum and Exponent functions

The Challenge I am facing is combining two formulas based for a game on command and Conquer. The Silo creates continuous productivity when left alone for a while with storage. Only looking at the upgrade and selling cost. In this case "tiberium"

how much each "silo" costs per level
how much total spent
how much it sells for at that level


etc.

found two essential formulas:

Partial Sum
Exponential function


Where Partial Sum is:

y=(n(n+1))/2


and Exponential formula

y=ab^x


where

y is the output.
a and b refer to the climbing curve of cost
and x which is the silo's level
n denotes infinite level of the silo base


For Example:

Upgrade Silo lv 9 to 10 costs 8800
Upgrade Silo Lv 8 to 9 costs 3200

The costs are the a and b where levels is the exponent power


Is this the correct way of writing the total cost of the silo at its current level? (forgive me if i dont know math shortcuts)

y=( ab^n ( ab^n + ab^1 ) ) / ab^2


If not, how do i correctly write the exponential function with the partial sum?

• Your question looks like this: "is this formula correct? follows a bunch of symbols without any explanation". How can we say if it's correct or not? What are these $a,b,n$? What are the rules these "silo" follow? Commented Nov 30, 2016 at 22:58
• thanks will edit Commented Nov 30, 2016 at 22:59
• what do you mean by "a and b refer to the climbing curve of cost"? and what units is "the silo's level" measured in? and what exactly is the silo base? Commented Nov 30, 2016 at 23:10
• currently trying to find a decent 'example' for the silos and how the levels are contributed. i will edit an example area to describe Commented Nov 30, 2016 at 23:37