f(x)=(2ax-a²+1)/(x²+1)
f'(x)=[2a(x²+1)-2x(2ax-a²+1)]/(x²+1)²
=(2ax²+2a-4ax²+2xa²-2x)/(x²+1)²
=2[-ax²+(a²-1)x+a]/(x²+1)²
=-2(x-a)(ax+1)/(x²+1)²
f'(x)=0 解得 x=a or x=-1/a
a>0时 a>-1/a
x0 f(x)递增
x>a 时 f'(x)
f(x)=(2ax-a²+1)/(x²+1)
f'(x)=[2a(x²+1)-2x(2ax-a²+1)]/(x²+1)²
=(2ax²+2a-4ax²+2xa²-2x)/(x²+1)²
=2[-ax²+(a²-1)x+a]/(x²+1)²
=-2(x-a)(ax+1)/(x²+1)²
f'(x)=0 解得 x=a or x=-1/a
a>0时 a>-1/a
x0 f(x)递增
x>a 时 f'(x)