càlcul diferencial

Si ( xe^{f(x)} = x & d_{x}[f(0)] = k ) ==> f(0) = 0

e^{f(x)}+xe^{f(x)}·d_{x}[f(x)] = 1

Si ( e^{x·f(x)} = x & d_{x}[f(0)] = k ) ==> f(0) = 1

e^{x·f(x)}( f(x)+x·d_{x}[f(x)] ) = 1