Question

函数y=－的反函数是

A.y=x²+1(x∈R)                                               B.y=x²+1(x>0)

C.y=x²+1(x≤0)                                                D.y=－x²+1(x≤0)

Answer 1

解析:由y=－(x≥1)知y≤0，且x－1=(－y)²,

即x=y²+1(y≤0).∴f^－1(x)=x²+1(x≤0).

答案:C