One (-4,3)

K 1=3/(c-4) K2=3/(-4-c)

AF 1 perpendicular to AF2.

K 1*K2 = - 1

c^2=25

F 1(-5，0) F2(5，0)

af 1 =√ 10 AF2 = 3√ 10

AF 1+AF2 = 4√ 10 =2a

a = 2√ 10

x^2/40 + y^2/ 15 = 1