Question

Derive the equation of the parabola with a focus at (4, −7) and a directrix of y = −15. Put the equation in standard form.

Answer 1

ok... have you plotted the information on the number plane so you know the concavity of the parabola..?

Answer 2

yeah

Answer 3

So, you can still use the combined distance equation for this problem. But you just have to make your solution ax^2+bx+c=0.

Answer 4

ax+by=c.

Answer 5

so is the directrix above or below the focus...? and then is the parabola concave up or down..?

Answer 6

so you plot looks like this

Answer 7

below right?

Answer 8

the distance is labelled 2a and is double the focal length.