Originally Posted by

**supaju** I've forgotten my math...

Is there an easier way to express the function in my title? Here's the context:

In Simcity you can buy a coal plant for $10000. Every year you own it it costs $1 per month * number of years owned * 12 months to maintain. If I've owned the plant for 20 years, it costed me $240 that year, $228 the previous year, $216 the year before that, etc. If I buy a new plant, the maintenance costs go back down to $12 for the year again. So what's the most affordable way to keep using coal plants?

I was thinking, let x = number of years between buying a new plant, and then I could come up with a function that tells me what the cost would be for every x years. It would be something like 10,000 + 12x + 12(x-1) + 12(x-2) and so on, but that's not so easy to evaluate for larger numbers.

So is there a way to simplify that expression? (Or should I just go wind power)?

Thanks in advance!