Question

Regan is trying to find the equation of a quadratic that has a focus of (−2, 5) and a directrix of y = 13. Describe to Regan your preferred method for deriving the equation. Make sure you use Regan's situation as a model to help her understand.

Answer 1

(-2,5) @surry99 can you help me with this please

Answer 2

http://hotmath.com/hotmath_help/topics/finding-the-equation-of-a-parabola-given-focus-and-directrix.html

Answer 3

but its negative

Answer 4

Are you referring to the -2?

Answer 5

yes i am

Answer 6

no problem...if you look at the general formula...
(x-a)^2 + b^2 - c^2 = 2(b-c)y

in your problem the focus is (-2, 5) which is (a, b) so..a = -2 and b =5
the directrix y =13 which is y=c...so c =13.
So plug these values in to the general formula and simplify.
(x - -2)^2 + 5^2 - 13^2 = 2(5-13)y... and (x--2) = (x+2) so...
(x+2)^2 +5^2 -13^2 = 2(5-13)y...now expand and simplify

Answer 7

thanks