第2课时　分段函数与映射

课后篇巩固提升

A组　基础巩固

1.下表表示y是x的函数,则函数的值域是(　　)

x 0

A.[2,5 B.N C.(0,20 D.{2,3,4,5}

解析:由题表可知,y={■(2"," 0

　　所以函数的值域为{2,3,4,5}.故选D.

答案:D

2.已知f:x→x2是集合A到集合B={0,1,4}的一个映射,则集合A中的元素最多有(　　)

A.3个 B.4个 C.5个 D.6个

解析:令x2=0,1,4,解得x=0,±1,±2.故选C.

答案:C

3.若f(x)={■(x"-" 3"," x≥10"," @f"(" f"(" x+6"))," x<10"," )┤则f(5)的值为(　　)

A.8 B.9 C.10 D.11

解析:由题意知,f(5)=f(f(11))=f(8)=f(f(14))=f(11)=8.故选A.

答案:A

4.函数f(x)={■(2x^2 "," 0≤x≤1"," @2"," 1