f_k(x)\,=\,\frac{x^2}{k^2}\, +\, \frac{k^2}{x^2}, \quad k>0

Näherungsfunktion

k = 2.5 (slider from 0 to 10, step 0.01)
f(x) = x^(2.0) / k^(2.0) + k^(2.0) / x^(2.0)
a = true
g(x) = 1.0 / k^(2.0) * x^(2.0)