A:Because he has to do his homework.
B:Because he hates to do the dishes.
C:Because he has to make his bed first.
分解因式:2x2﹣4x+2=____.
下图为某地区等高线地形图。读图,回答问题。
函数y=1-x中自变量x的取值范围是____ .
一个装盛某种液体的圆柱形铁桶,其中央纵截面是边长为a的正方形,如图16所示.当桶内没有液体时,从某点A恰能看到桶底边缘的某点B.当桶内液体的深度为桶高的 34 时,仍沿AB方向看去,恰好看到桶底上的C点,C、B两点相距 14 a,求该液体的折射率(最后结果可用根式表示).