计算:(x+y)(x-y)(x2-y2)。
解:原式=(x2-y2)(x2-y2)=(x2-y2)2=x4-2x2y2+y4。
根据句子意思及所给提示完成下面各题。
1. My father often _____ ( go) home at 7 p. m.
2. My mother often _____ ( do) some shopping on Saturdays.
3. I often surf the Internet _____ ( one) a week.
4. How often _____ she _____ (exercise)?
一头奶牛,5岁,最近表现转圈运动,触诊额骨变薄、松软,皮肤隆起。
如手术治疗该病,则不可采用的皮肤切口形状是()。
A、“工”字形
B、“十”字形
C、“U”字形
D、“1”字形
E、圆形