Having Trouble finding the Focus and Directrix of a Parabola

colender

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Jul 15, 2012
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I am having a hard time trying to solve a problem that is in my book, which ask to find the vertex,focus, and directrix of a parabola in standard form give (h,k). I have been able to find the vertex but I keep having trouble finding the focus.

(2x-4)^2 = (8y-16)
this is the problem I know I have to factor out the 2 and the 8

2(x-2)^2 = 8(y-2) which gets me the vertex (2,2)

then if I try this

(x-2)^2 = 8/2(y-2)

4p = 8/2 = p=1
I know the answer for the focus is (2,5/2) but I don't know how they got p= 1/2. Am i missing something here I don't know what I am doing wrong.


Much help needed but thanks in Advance
 
I am having a hard time trying to solve a problem that is in my book, which ask to find the vertex,focus, and directrix of a parabola in standard form give (h,k). I have been able to find the vertex but I keep having trouble finding the focus.

(2x-4)^2 = (8y-16)
this is the problem I know I have to factor out the 2 and the 8

2^2(x-2)^2 = 8(y-2) which gets me the vertex (2,2) <-- you have to factor out 2^2 = 4

then if I try this

(x-2)^2 = 8/2(y-2)

4p = 8/2 = p=1
I know the answer for the focus is (2,5/2) but I don't know how they got p= 1/2. Am i missing something here I don't know what I am doing wrong.


Much help needed but thanks in Advance
...
 
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