Question

若f(x)=(e^x－e^－x)，g(x)=(e^x+e^－x)，则f(2x)等于

A.2f(x)                                                            B.2g(x)

C.2［f(x)+g(x)］                                             D.2f(x)·g(x)

Answer 1

解析:2f(x)·g(x)=2·(e^x－e^－x)·(e^x+e^－x)

=(e^2x－e^－2x)=f(2x).

答案:D