题目内容
观察下列各题的运算①![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/201310201208004534294606/SYS201310201208004534294012_ST/0.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/201310201208004534294606/SYS201310201208004534294012_ST/1.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/201310201208004534294606/SYS201310201208004534294012_ST/2.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/201310201208004534294606/SYS201310201208004534294012_ST/3.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/201310201208004534294606/SYS201310201208004534294012_ST/4.png)
【答案】分析:分别利用二次根式的性质、单项式之间的乘法、数的0次幂、绝对值的性质进行计算即可.
解答:解:①
=-
;
②(3a2b)2•2b3=9a4b2•2b3=18a4b5;
③a=1(a≠0);
④
=a4;
⑤(-7
)2=49×
=14;
⑥|4
-7|=7-4
.
∴其中计算正确的有⑤⑥.
点评:主要考查了二次根式的化简.注意最简二次根式的条件是:①被开方数的因数是整数,因式是整式. ②被开方数中不含能开得尽方的因数因式.上述两个条件同时具备(缺一不可)的二次根式叫最简二次根式.
解答:解:①
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/201310201208004534294606/SYS201310201208004534294012_DA/0.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/201310201208004534294606/SYS201310201208004534294012_DA/1.png)
②(3a2b)2•2b3=9a4b2•2b3=18a4b5;
③a=1(a≠0);
④
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/201310201208004534294606/SYS201310201208004534294012_DA/2.png)
⑤(-7
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/201310201208004534294606/SYS201310201208004534294012_DA/3.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/201310201208004534294606/SYS201310201208004534294012_DA/4.png)
⑥|4
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/201310201208004534294606/SYS201310201208004534294012_DA/5.png)
![](http://thumb.1010pic.com/pic6/res/czsx/web/STSource/201310201208004534294606/SYS201310201208004534294012_DA/6.png)
∴其中计算正确的有⑤⑥.
点评:主要考查了二次根式的化简.注意最简二次根式的条件是:①被开方数的因数是整数,因式是整式. ②被开方数中不含能开得尽方的因数因式.上述两个条件同时具备(缺一不可)的二次根式叫最简二次根式.
![](http://thumb2018.1010pic.com/images/loading.gif)
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