分解因式:
(1)x3-x;
(2)-2x+x2+1.
(1)x3-x
=x(x2-1)
=x(x+1)(x-1);
(2)-2x+x2+1=(x-1)2.
单词归类:将下列各组属于同一类别的单词找出,并写在相应的横线上;不属于该类别的写在括号内。
( )1. 职业类:actor tiger teacher angry dentist ___________________________
( )2. 电器类:floor light radio paper computer ___________________________
( )3. 食物类:noodle bread taste cake jacket ___________________________
( )4. 植物类:plane flower grass ram leaf ___________________________
农田生态系统处于生态系统演替的早期阶段。( )