Question

已知圆C:(x+2)^2 +(y-6)^2 =36 (2)是否存在直线l,使l过点(-4,0),并与圆D交与P,Q两点,

Answer 1

设Q(a,b),则QI=（-4-a,-b）,设PI=uQI,则P的坐标为(4-4u-au,-ub),于是有：OP*OQ=a(4-4u-au)+b(-ub)=4a-4au-a^2*u-u*b^2=24,同时（a+2）^2+(b-6)^2=36,(6-4u-au)^2+(-6-ub)^2=36,