Simple Math question


Any tip or tutorials for doing exp/log.

I get the programming but it's been a while since I did math.

example: To make alpha fade away on smoke, there's linear way of just "image_alpha-=.01"

but to make it fade away in the same time, but quickly in the start and then slower towards the end, or vice versa, what's the particular formula for something like that.

I've been messing around but I can't seem to really notice the differences, and I am not sure what I am doing.

I am sure there's someone here that knows math. I could figure out the answers to problems, but I don't even know how to write the problem from scratch.