f(x)= e2x-4*ex
e^{2x} - 4*e^x = 0
e^{2x} = 4*e^x | : e^x
e^x = 4
f ´( x ) = e^{2x} * 2 - 4* e^x
e^{2x} * 2 - 4* e^x = 0
e^{2x} * 2 = 4* e^x | : e^x
e^x * 2 = 4
e^x = 2
f ´´( x ) = e^{2x} * 2 * 2 - 4* e^x
e^{2x} * 4 - 4* e^x = 0
e^{2x} * 4 = 4* e^x | : e^x
e^x * 4 = 4
e^x = 1