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设实数a,b,x,y满足a2+b2=1,x2+y2=3, 则ax+by的取值范围为_______________.
设O为坐标原点,点A.(1,1),若点B(x,y)满足,则取得最小值时,点B的个数是( )
A. 1 B. 2 C.3 D.无数个