5．We have several a________to choose from.

4．Husband and wife should s________roles with each other occasionally.

3．The officer c________his men to fire.

2．When I got to the railway station，they were l________the truck with bananas.

1．Oil is Kuwait’s most important natural r________.

6. 已知a、b、c均為實(shí)數(shù)，且=c。

化簡。

5．對于題目“化簡求值：+，其中a=”，甲、乙兩個學(xué)生的解答不同．

　　 甲的解答是：+=+=+－a=

　　 乙的解答是：+=+=+a－=a=

　　 誰的解答是錯誤的？為什么？

4.已知x=+1，求()÷的值．

2.計(jì)算：(3+。

3(.如圖所示，實(shí)數(shù)a，b在數(shù)軸上的位置，化簡．

1.計(jì)算：+(－)+。