求取值的范围
设f(x)=x^-x+k,log2(f(a))=2,f(log2(a))=k(a≠1),
(1)求f(log2(x))的最小值及相应的x,
(2)若f(log2(x))>f(1),且log2(f(x))f(1)=2,即:[log2(x)]^-log2(x)+2>2
log2(x)1
∴02……②
又由于log2(f(x))<2,且f(x)≥7/4即:f(x)<4,x^-x+2<4,
∴-1
设f(x)=x^-x+k,log2(f(a))=2,f(log2(a))=k(a≠1),
(1)求f(log2(x))的最小值及相应的x,
(2)若f(log2(x))>f(1),且log2(f(x))f(1)=2,即:[log2(x)]^-log2(x)+2>2
log2(x)1
∴02……②
又由于log2(f(x))<2,且f(x)≥7/4即:f(x)<4,x^-x+2<4,
∴-1 收起