y=ln [2+根号(x^2+4)]/x
y=ln [2+根号(x^2+4)]-lnx
所以
y'=1/[2+根号(x^2+4)]*[2+根号(x^2+4)]'-1/x
=[x/√(x^2+4)]/[2+√(x^2+4)]-1/x
=x/[2√(x^2+4)+x^2+4]-1/x
y=ln [2+根号(x^2+4)]/x
y=ln [2+根号(x^2+4)]-lnx
所以
y'=1/[2+根号(x^2+4)]*[2+根号(x^2+4)]'-1/x
=[x/√(x^2+4)]/[2+√(x^2+4)]-1/x
=x/[2√(x^2+4)+x^2+4]-1/x