设 P(a^2/c,p),F1（-c,0),F2(c,0)∵存在P使线段PF1的中垂线过点F2∴F1F2=PF2∴4c^2=(a^2/c-c)^2+p^2∵p^2≥0∴4c^2≥(a^2/c-c)^2∴3c^4+2a^2c^2-a^4≥0两边同时除以a^4得 3e^4+2e^2-1≥0e^2≥1/3 (e^2≤-1舍去）∴ e...