three years，I have taken part in many activities with my classmates．But I think the Clean﹣up Day is the most unforgettable of all the things that have happened．（高分句型一）（开篇点题）
On the afternoon of a sunny day，all of my classmates took the tools and went to the playground．Some of us swept the floor，some picked the litter up and the others watered the flowers．（具体地经历）
At last，the whole school became brighter and cleaner．All of us felt very tired but we still felt very happy，because we all gave our own energy to make the school become better and better．（高分句型二）（收获和感想）
置颠倒（x的系数作分母）；解方程组时：每一步只作一种变形，一步步来，不要跨度太大而出错，解完可以带入原方程检验对不对；解不等式、不等式组：严格按步骤去做，注意解集的确定，要利用数轴正确定解集；易错点：①去分母时漏乘不含分母项（整数项也要乘以最小公倍数）；②去括号时漏乘（没乘遍每一项）、部分项忘记变号（要变号都变号）；③移项忘记变号；④将未知数系数化为1时分子分母位
