What is the equation of the parabola, in vertex form, with focus at (1,-4) and
directrix x= 3?

Answer:
D.
Step-by-step explanation:
1) according to the definition of parabola d(focus)=f(directrix),
2) then
[tex]d(focus)=\sqrt{(x-1)^2+(y+4)^2} \ and \ d(directrix)=|x-3|;[/tex]
[tex]\sqrt{(x-1)^2+(y+4)^2} =|x-3|;[/tex]
3) after evoluation the equation:
(y+4)²=-4x+8 or (y+4)²= -4(x-2);
4) correct answer is D.