f(x)=lnx+a/(x+1)所以x>0且x不等于-1当a=9/2,g(x)=f(x)-k=lnx+9/2(x+1)-k g'(x)=1/x-9/[2(x+1)^2]=(2x-1)(x-2)/[x(x+1)^2]令g(x)=0,即(2x-1)(x-2)/[x(x+1)^2]=0解得：x=1/2或x=2当0