楼上有一处算错了.由焦半径公式r1=a+ex1 r2=a+ex2|MN|=2a+e(x1+x2)=2b由已知a=3 b=1 c=2√2x1+x2=2a(b-a)/c=-3/√2设直线方程y=k(x+2√2）x^2+9y^2=9联立（9k²+1)x²+36√2k²x+72k²-9=0x1+x2=-36...