题目

用括号里所给单词的适当形式填空 1. Look! They’re        (ride) camels. 2. Thanks for        (join) our basketball match. 3. It looks like rain. It’s        (cloud). 4. Everyone         (do) some cleaning every day. 5. Look! They’re taking         (photo) over there. 答案：1.riding 2.joining 3.cloudy 4.does 5.photos3．先化简，再求值：$\frac{a-b}{a+b}$÷$\frac{{a}^{2}+{b}^{2}}{{a}^{2}-{b}^{2}}$-$\frac{a+b}{ab}$•$\frac{{a}^{2}b+a{b}^{2}}{{a}^{2}{+b}^{2}}$，其中|a+$\frac{1}{2}$|与b2-4b+4互为相反数．