|
Question 703270: Find the equation in standard form of the given parabola as a conic section. Focus is at (-2, 5) Directrix is y=1
Answer by AnlytcPhil(1806) (Show Source):
You can put this solution on YOUR website! Find the equation in standard form of the given parabola as a conic section. Focus is at (-2, 5) Directrix is y=1.
That will either be
(x-h)² = 4p(y-k), if the parabola is like a U or an upside down U.
or it will be
(y-k)² = 4p(x-h), if the parabola is like a C or a backwards C.
where (h,k) is the vertex and p is the distance from the vertex
to the focus and also the distance from the vertex to the
directrix. p is taken positive is like a U or a C, and negative
if it is like an upside-down U or a backwards C.
First we will sketch the graph:
Plot the focus and graph the directrix:
Draw a line from the focus straight down through the vertex
all the way to the directrix:
Now sketchin the parabola through the vertex and the upper
outer corners of those two squares, like this:
So the parabola is like a U so it has the form:
(x-h)² = 4p(y-k) and p is taken positive.
The vertex is V(h,k) = V(-2,3) and p is the distance from the vertex to
the focus and also the distance from the vertex to the
directrix which is p=2, so substitute h=-2,k=3,p=2:
(x-(-2))² = 4(2)(y-3)
(x+2)² = 8(y-3)
Edwin
|
|
|
| |