1. The problem statement, all variables and given/known data
I first posted this in the pre-calculus section, then the guy who first came up with the formula hinted at integration, so I guess it's meant to be in the calculus section

Now this isn't a homework question, it's something me and some others are looking into, and someone posted this function, and I'm not sure how he worked it out:

So what he's done is used the figures from the albums certified to create an equation. So therefore if you substitute 1 for x in the function, which is actually equal to 500,000 you will get all the albums that certified for over 500,000 sales, it's not exact, but it's a close enough function, how did he work that function out?

Probably just drew a graph and concentrated on the points that seemed to fit a smooth curve. Adjusted a and b in f(x)=1/(ax+b) to fit it. You can use least squares type techniques to help to you estimate the constants. But I'm confused. I put x=1 into 1/(1.23*x+0.278) and I get 0.663. That's not 67. Do you mean I should multiply by 100 also?

Yea you have to multiply by 100, I got 66.3 too, but I guess he rounded up, not sure why he rounded up, but the other values seems to indicate that's what he did.

Like I said, you can use least squares to fit almost any smooth curve pretty well. Especially if you start throwing out points that don't fit. And use creative rounding to boot.