### How to find parameter functions ?

Is given y = f(x). How to find x = fx(u) and y = fy(u) where u is uniform by length of curve.

Especially I interested in functions:

$f\left(x\right)\ =\ \frac{\sqrt{\left[\left(d\cdot x\right)^{d}\cdot\frac{c^{c}}{\left(d\cdot x+c\right)^{\left(d+c\right)}}\right]}}{x}$
and
$f\left(x\right)\ =\ \frac{\left(b-\frac{a}{x\ -c}\right)}{\left(x-c\right)}$