f(-x)=-2x/(x^2+1)=-f(x)
所以為奇函數(shù)
f'= (2(x^2+1)-2x(2x))/(x^2+1)^2
= 2(1-x^2)/(x^2+1)^2
=2(1-x)(1+x)/(x^2+1)^2
所以[-1,1]單調(diào)遞增
(-無窮,-1) (1,+無窮)單調(diào)遞減
最大值f(1)=1
最小值f(-1)=-1
f(-x)=-2x/(x^2+1)=-f(x)
所以為奇函數(shù)
f'= (2(x^2+1)-2x(2x))/(x^2+1)^2
= 2(1-x^2)/(x^2+1)^2
=2(1-x)(1+x)/(x^2+1)^2
所以[-1,1]單調(diào)遞增
(-無窮,-1) (1,+無窮)單調(diào)遞減
最大值f(1)=1
最小值f(-1)=-1