Find the equation of hyperbola whose foci are $F_1 = (3, 4)$ and $F_2 = (-1,-2)$ and $a=1$? 
Find the equation of hyperbola whose foci are $F_1 = (3, 4)$ and $F_2 = (-1,-2)$ and $a=1$?

I need some help with this exercise. I know that this hyperbola is not centered at the origin, but I don't know its orientation and consequently the form of its equation. Does the distance between the foci still $2c$ in this case?

Apply the definition, directly
$PF_1-PF_2=2a$
$$\sqrt{(x-3)^2+(y-4)^2}-\sqrt{(x+1)^2+(y+2)^2}=2$$
$$\sqrt{x^2-6 x+y^2-8 y+25}=\sqrt{x^2+2 x+y^2+4 y+5}+2$$
and square both sides
$$x^2-6 x+y^2-8 y+25=x^2+2 x+y^2+4 y+9+4 \sqrt{(x+1)^2+(y+2)^2}$$
Rearrange  and divide both sides by $4$
$$4 - 2 x - 3 y=\sqrt{x^2+2 x+y^2+4 y+5}$$
and square again
$$\color{red}{3 x^2+8 y^2+12 x y-18 x-28 y+11=0}$$
is the equation of the wanted hyperbola.
Hope this can be useful
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