f(x)=x^a-x
导数为
f'(x)=a*x^(a-1)-1
假设a>0,
（1）a为偶数时,f'(x)=a*x^(a-1)-1在R上单调递增.
令f'(x)=a*x^(a-1)-1=0 得
x=(1/a)^(1/(a-1))
则f(x)=x^a-x在（-无穷,(1/a)^(1/(a-1))]上递减,在（(1/a)^(1/(a-1)),+无穷)上递增.
(2)a为奇数时,f'(x)=a*x^(a-1)-1是开口向上的偶函数,在-(1/a)^(1/(a-1))
函数f(x)=x^-x的单调递减区间是
0,（1）a为偶数时,f'(x)=a*x^(a-1)-1在R上单调递增.令f'(x"}}}'>