Find the standard form of the equation of the parabola with a focus at (0, 8) and a directrix at y = -8.

Question

hero · Answer

You're given two points: the focus (0,8) and directix (x,-8). Insert them in to this formula:

$(x - x_1)^2 + (y - y_1)^2 = (x - x_2)^2 + (y - y_2)^2$

Then simplify

anonymous · Answer

is it y2=8x @Hero ?

hero · Answer

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anonymous · Answer

thank you so much! that website was pretty cool too! @Hero

hero · Answer

Did you understand every step?

anonymous · Answer

yes i see what i did wrong that was helpful

hero · Answer

What rule did I use to get from 

$(y + 8)^2 - (y - 8)^2$  to $(y + 8 + y - 8)(y + 8 - (y - 8))$ ?

anonymous · Answer

didnt you just expand?

hero · Answer

Nope. I used Difference of Squares:

$a^2 - b^2 = (a + b)(a - b)$