A.7

B.10

C.5

D.8

解析:∵x1=2,x2=3,

∴x1≠x2.

∴y=x1+x2=2+3=5.

答案:C

7.运行下列算法语句后,输出的结果为　　　　　.

x=-1

y=20

If x<0 Then

　x=y+3

Else

　y=y-3

End If

输出x-y,x+y.

解析:因为x=-1<0,

所以x=20+3=23.

因为y=20,所以x-y=3,x+y=43.

答案:3,43

8.执行如下算法语句:

输入x;

If　x>=0　Then

　y=x2-6x+11

Else

　y=x2+10x+27

End If

输出y.

要使输出的y值最小,则输入的x的值为　　　　　.

解析:执行此算法语句的功能是求函数y={■(x^2 "-" 6x+11"," x≥0"," @x^2+10x+27"," x<0)┤的函数值.

由函数的性质知,当x=3或x=-5时,y有最小值2.

答案:3或-5

9.已知符号函数y=sgn x的定义为y={■(1"," x>0"," @0"," x=0"," @"-" 1"," x<0"," )┤试编写算法语句,使输入x的值输出相应y的值.

解算法语句如下:

输入x;

If　x>0　Then