已知f(x)=aa2?1(ax?a?x) (a>0且a≠1).(Ⅰ)判断f(x)的奇偶性;(Ⅱ)判断f(x)的单调性,并证明你

2025-06-22 11:01:04
推荐回答(1个)
回答1:

( I)函数定义域为R,
f(x)=

a
a2?1
(ax?a?x) (a>0且a≠1).
f(?x)=
a
a2?1
(a?x?ax)=?f(x)

∴f(x)为奇函数.
( II)设x1,x2∈R且x1<x2
f(x1)?f(x2)=
a
a2?1
[(ax1?a?x1)?(ax2?a?x2)]
=
a
a2?1
(ax1?ax2+a?x2?a?x1)=
a
a2?1
(ax1?ax2+
1
ax2
?
1
ax1
)

=
a
a2?1
(ax1?ax2+
ax1?ax2
ax1+x2
)=
a
(a+1)(a?1)
(ax1?ax2)(1+
1
ax1+x2
)

当a>1时,
a
(a+1)(a?1)
>0,ax1?a