Question

函数y=0.2^－x+1的反函数是

A.y=log₅x+1                                                     B.y=log_x5+1

C.y=log₅(x－1)                                                 D.y=log₅x－1

Answer 1

解析:由y=0.2^－x+1得y－1=5^x,

即x=log₅(y－1).

∴f^－1(x)=log₅(x－1)(x＞1).

答案:C