雙曲線x^225-y^29=1,求過點(6,-1)的動弦的中點所在的軌跡方程
- 2022-07-02
動弦AB的中點P(x,y)
xA+xB=2x,yA+yB=2y
k(AB)=(yA-yB)/(xA-xB)=(y+1)/(x-6)
[(xA)^2/25-yA)^2/9]-[(xB)^2/25-(yB)^2/9]=1-1=0
(xA+xB)*(xA-xB)/25-(yA+yB)*(yA-yB)/9=0
2x/25-2y*(yA-yB)/[9(xA-xB)]=0
x/25-y*(y+1)/[9(x-6)]=0
x*(x-6)/25-y*(y+1)/9=0
(x-3)^2/25-(y+0。5)^2/9=299/900
(x-3)^2/(299/36)-(y+0。5)^2/(299/100)=1