A:For the first time
B:By the first time
C:At the first time
D:The first time
心脏四个腔中,心脏壁最厚的腔以及与之相连的血管分别是( )
复数z满足z•z-+z+z-=17,则|z+2﹣i|的最小值为( )
满足方程组2x+y=m+2x-y=m的x,y的值的和等于2,求x,y,m的值.