a²=5b²=4所以c²=5-4=1c=1所以F(-1,0)若斜率不存在,x=-1则中点是(-1,0)斜率存在是y=k(x+1)=kx+k代入4x²+5y²=20(4+5k²)x+10k²x+5k²-20=0x1+x2=-10k²/(4+5k²)y=kx+k...