Question

方程为xˆ2/aˆ2+yˆ2/bˆ2=1(a＞b＞0)的椭圆左顶点为A,左右交点

Answer 1

假定D（0,b)

3DF1向量=DA向量+2DF2向量即3(-c,-b)=(-a,-b)+2(c,-b)

即(-3c,-3b)=(-a+2c,-3b,),

所以-3c=-a+2c,a=5c,e=1/5