The green line is the plot of

`f(x) = 6100000/x`

, or, to put it another way, the plot of `x × y = 6100000`

. The knee in the curve ought to be where `x = y = √6100000 ≈ 2470`

. But look at the chart! Just by eyeballing it, we can see that 2470 is nowhere near what anyone would call the knee.
## 2 comments:

It's a smooth curve; the illusion of a "knee" is only because of the scale you've plotted it on. If you plot it such that the x and y axes are equally scaled, the visual "knee" will appear to be where you expect it.

Exactly right. If you change the scale of x and y you will find that you can put the "knee" anywhere on the curve you want.

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