问题 填空题
已知A(-1,0),B(1,0),点C、点D满足|
AC
|=4,
AD
=
1
2
(
AB
+
AC
)
,则点C的轨迹方程是______;点D的轨迹方程是______.
答案

设C、D点的坐标分别为C(x0,y0),D(x,y),

AC
=(x0+1,y0),
AB
=(2,0),

AB
+
AC
=(x0+3,y0),

AD
=
1
2
(
AB
+
AC
)=(
x0+3
2
y0
2

AD
=(x+1,y).

x0=2x-1
y0=2y

代入|

AC
|=
(x0+1)2+y02
=4,整理得x2+y2=4,

点D的轨迹方程为x2+y2=4

x=
x0+1
2
y=
y0
2

代入x2+y2=4得(x+1)2+y2=16

∴点D的轨迹方程为(x+1)2+y2=16

故答案为(x+1)2+y2=16,x2+y2=4,

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