Źródło TeX:

f^{\prime }(x)=0\;\Leftrightarrow \;\frac{\left( x-1\right) \left( x+1\right) }{x^{2}\left( x^{2}+1\right) }=0\;\Leftrightarrow\; \left( x-1\right) \left( x+1\right) =0 \; \Leftrightarrow\; (x=-1\vee x=1)