【答案】
分析:两个含有根式的代数式相乘,如果它们的积不含有根式,那么这两个代数式相互叫做有理化因式.根据有理化因式的定义判断各个选项,得出正确结果.
解答:解:(A)(
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194432006992874/SYS201311031944320069928005_DA/0.png)
+1)(1-
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194432006992874/SYS201311031944320069928005_DA/1.png)
)=1-3x,满足有理化因式的定义,正确;
(B)(
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194432006992874/SYS201311031944320069928005_DA/2.png)
+y)(-
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194432006992874/SYS201311031944320069928005_DA/3.png)
-y)=-(x+y
2+2y
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194432006992874/SYS201311031944320069928005_DA/4.png)
),不满足有理化因式的定义,错误;
(C)(2-
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194432006992874/SYS201311031944320069928005_DA/5.png)
)(
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194432006992874/SYS201311031944320069928005_DA/6.png)
-2)=4
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194432006992874/SYS201311031944320069928005_DA/7.png)
-x-4,不满足有理化因式的定义,错误;
(D)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194432006992874/SYS201311031944320069928005_DA/8.png)
•
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194432006992874/SYS201311031944320069928005_DA/9.png)
x=
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/20131103194432006992874/SYS201311031944320069928005_DA/10.png)
,不满足有理化因式的定义,错误;
故选(A).
点评:本题考查有理化因式的定义,正确计算是解题的关键.