1)定义域为x>0
f'(x)=1/x+2ax+b=(2ax^2+bx+1)/x
f'(1)=1+2a+b=0,得b=-2a-1
即f'(x)=[2ax^2-(2a+1)x+1]/x=(x-1)(2ax-1)/x
讨论a:
当0