函数12

1)f(a)=4 ===>a^-a+b=4 ......(1)

由且....===>[log(2,a)]^2 -log(2,a)=0
log(2,a)[log(2,a)-1]=0
a不等于1 ====>a=2
代入(1)=========>b=2

2)f(x)=x^2-x+2 =(x-1/2)^2 + 7/4 >0
f(1)=2 f(0)=2
==>在x>1时,f(x)是增函数
x<0时 f(x)>2
f[log(2,x)]>f(1)===>log(2,x)>1
===>x>2
或
f[log(2,x)]<0 ===>0<x<2 ......(2)

f(1)=2
log[2,f(x)]<f(1)
===>log[2,f(x)]<2 ===>f(x)<4
===>x^2-x+2<4===>-2<x<2 .......(3)

====>(2),(3)交集 ====> 0<x<2