分解因式:5x2-20=______.
5x2-20,
=5(x2-4),
=5(x+2)(x-2).
故答案为:5(x+2)(x-2).
根据课本P47 的课文回答下列问题。
1. Who wrote this letter?
____________________
2. Who is this letter to?
3. How old is the writer?
4. The diary is specil, isn't it?
水稻晒田的作用有()。
A、更新土壤环境,促进根系生长,增强根系活力
B、提高土壤温度,促进水稻分蘖
C、减少土壤水分,增加土壤中空气,为水稻生长提供足够氧气
D、控制杂草生长,缓解水稻和杂草争肥的矛盾