函数f(x)的定义域为R,并满足条件:①对任意x∈R,有f(x)>0;②对任意x,y∈R,有f(x•y)=[f(x)]y;③f(13)>1.(1)求f(0)的值;(2)求证:f(x)在R上是单调递增函

题目简介

函数f(x)的定义域为R,并满足条件:①对任意x∈R,有f(x)>0;②对任意x,y∈R,有f(x•y)=[f(x)]y;③f(13)>1.(1)求f(0)的值;(2)求证:f(x)在R上是单调递增函

题目详情

函数f(x)的定义域为R,并满足条件:
①对任意x∈R,有f(x)>0;
②对任意x,y∈R,有f(x•y)=[f(x)]y
f(
1
3
)>1

(1)求f(0)的值;   
(2)求证:f(x)在R上是单调递增函数.
题型:解答题难度:中档来源:不详

答案

(1)令x=0,y=2,则f(0)=[f(0)]2
∵f(0)>0,∴f(0)=1
(2)任取x1,x2∈R,且x1<x2
x1=class="stub"1
3
P1x2=class="stub"1
3
P2
,则P1<P2
f(x1)-f(x2)=f(class="stub"1
3
P1)-f(class="stub"1
3
P2)=[f(class="stub"1
3
)]P1-[f(class="stub"1
3
)]P2

f(class="stub"1
3
)>1,P1P2
,∴[f(class="stub"1
3
)]P1<[f(class="stub"1
3
)]P2

∴f(x1)<f(x2),∴f(x)在R上是单调递增函数.

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