已知:A=x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
+xy+y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
,B=-3xy-x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
求(1)B-A;(2)2A-3B;(3)若A-B-C=0,則C如何用含x,y的代數(shù)式表示?
(1)-2x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
-4xy-y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
;(2)5x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
+11xy+2y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
;(3)2x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
+4xy+y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
試題分析:先根據(jù)題意分別列出代數(shù)式,再去括號、合并同類項即可.
(1)B-A=(-3xy-x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
)-(x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
+xy+y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
)=-3xy-x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
-x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
-xy-y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
=-2x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
-4xy-y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
;
(2)2A-3B=2(x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
+xy+y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
)-3(-3xy-x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
)=2x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
+2xy+2y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
+9xy+3x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
=5x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
+11xy+2y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
;
(3)∵A-B-C=0
∴C= A-B=(x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
+xy+y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
)-(-3xy-x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
)=x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
+xy+y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
+3xy+x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
= 2x
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
+4xy+y
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823023524643242.png)
.
點評:解題的關(guān)鍵是熟練掌握在去括號時,若括號前是“-”號,把括號和括號前的“-”號去掉后,括號里各項的符號均要改變.
練習(xí)冊系列答案
相關(guān)習(xí)題
科目:初中數(shù)學(xué)
來源:不詳
題型:解答題
先去括號,再合并同類項:
![](http://thumb.zyjl.cn/pic2/upload/papers/20140823/20140823033509841564.png)
。
查看答案和解析>>
科目:初中數(shù)學(xué)
來源:不詳
題型:填空題
多項式3a2b2-5ab2+a2-6是___次 項式,常數(shù)項是 .
查看答案和解析>>
科目:初中數(shù)學(xué)
來源:不詳
題型:填空題
如果a-3b=-3,那么代數(shù)式5-a+3b=
查看答案和解析>>
科目:初中數(shù)學(xué)
來源:不詳
題型:單選題
“少年宮”樓階梯教室,第一排有m個座位,后面每一排都比前面一排多4個座位,則第n排座位數(shù)是( )
A.m+4 | B.m+4n | C.n+4(m-1) | D.m+4(n-1) |
查看答案和解析>>