Thank you for the opportunity to help you with your question!
Let ( x0 , y0 ) be any point on the parabola.
Find the distance between (x0 , y0) and the focus. Then find the distance between (x0 , y0) and directrix. Equate these two distance equations and the simplified equation in x0 and y0 is equation of the parabola.
The distance between (x0 , y0) and (2, -1) is
sqrt((x-2)^2 + (y-(-1))^2)
(x0 , y0) and the directrix, y = -1/2 is
| y0– -1/2|.
Equate the two distance expressions and square on both sides.
(x-2)^2 + (y-(-1))^2) = (y+1/2)^2
answer is D.
Please let me know if you need any clarification. I'm always happy to answer your questions.
Jul 10th, 2015
Are you studying on the go? Check out our FREE app and post questions on the fly!