A:had been pointing
B:have been pointing
C:were pointing
D:pointed
设方程x2+y2﹣2mx﹣2m2y+m4+2m2﹣m=0表示一个圆.
(1)求m的取值范围;
(2)m取何值时,圆的半径最大?并求出最大半径.