Question

函數(shù)在上單調(diào)，則實(shí)數(shù)的取值范圍是 (      )

A．

B．

C．

D．

Answer 1

A

本題考查分段函數(shù)的含義，分段函數(shù)的單調(diào)性，二次函數(shù)和指數(shù)函數(shù)的性質(zhì).
要使函數(shù)在上單調(diào)，需使函數(shù)分別在和上的單調(diào)性一致，并且分段函數(shù)在分段處滿足該單調(diào)性；
（1）當(dāng)時，函數(shù)在上是增函數(shù)，要使函數(shù)在上單調(diào)，需單調(diào)遞增；則實(shí)數(shù)滿足解得

（2）當(dāng)時，函數(shù)在上是減函數(shù)，要使函數(shù)在上單調(diào)，需單調(diào)遞減；則實(shí)數(shù)滿足解得

綜上：實(shí)數(shù)的取值范圍是  .故選A