设M点坐标(X,Y)
DM:DP=3:2,DM=Y,DM=2/3Y,M点坐标为(X,2/3Y)
又P在圆上,x^2+y^2=4,X^2+(2/3Y)^2=4
9X^2+4Y^2=36
X^2/4+Y^2/9=1
M点的轨迹为椭圆