已知半径为1的动圆与圆(x-5)2+(y+7)2=16相切,则动圆圆心的轨迹方程是( )
A.(x-5)2+(y+7)2="25" | B.(x-5)2+(y+7)2=17或(x-5)2+(y+7)2=15 |
C.(x-5)2+(y+7)2="9" | D.(x-5)2+(y+7)2=25或(x-5)2+(y+7)2=9 |
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已知半径为1的动圆与圆(x-5)2+(y+7)2=16相切,则动圆圆心的轨迹方程是( )
A.(x-5)2+(y+7)2="25" | B.(x-5)2+(y+7)2=17或(x-5)2+(y+7)2=15 |
C.(x-5)2+(y+7)2="9" | D.(x-5)2+(y+7)2=25或(x-5)2+(y+7)2=9 |