The challenges of managing breast cancer in the developing world - a perspective from sub-Saharan Africa Communicable diseases are the major cause of mortality in lower-income countries. Consequently, local and international resources are channelled mainly int... J, Edge,I, Buccimazza,H, Cubasch...
,因为M是线段PN的中点,所以 , 又因为M,N是圆上的任意两点,则有0< ≤2r,即0< ≤8r2. 设动点P(x,y),圆心C坐标为(3,2),则有0<(x-3)2+(y-2)2-r2≤8r2,即r2<(x-3)2+(y-2)2≤9r2,在一个圆环内,又因为P在直线3x+y=3上,所以直线3x+y=3与圆环有公共点,即直线与圆(x-3)2+(y-...