Question

设函数f(x)＝2?x?1，x≤0log2x，x＞0，则f(f(12))=______

设函数f(x)＝2?x?1，x≤0log2x，x＞0，则f(f(12))=______．

Answer 1

∵

1

2

＞0，∴f(

1

2

)＝log2

1

2

=-1，
∵-1＜0，∴f（-1）=2^-（-1）-1=2-1=1．
∴f(f(

1

2

))＝f(?1)＝1．
故答案为1．