Question

已知函数f(x)=（x-a)/x－lnx.

Answer 1

f(x)=1-a/x－lnx.f′(x)=a/(x^2)-1/x=(a-x)/(x^2),(x>0)

(1)a=2时,f′(x)=(2-x)/(x^2),(x>0),所以在(0,2),f′(x)>0,在(2,+∞)f′(x)0时,f′(x)=(a-x)/(x^2)0时,f′(x)=(a-x)/(x^2),(x>0),所以在(0,a),f′(x)>0,在(a,+∞)f′(x)