What Is the General Equation of a Parabola with Directrix x=p and Focus (h, k)?

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SUMMARY

The general equation of a parabola with a directrix defined by x=p and a focus at (h, k) is accurately represented by the formula x=1/2(h-p) [y^2 - 2yk + h^2 + k^2 - p^2]. The vertex of this parabola is located at ((h+p)/2, k), and the focal length is calculated as (h-p)/2. The standard form of a horizontally oriented parabola is expressed as 4d(x - x_0) = (y - y_0)^2, which can be transformed into the derived equation. This confirms the correctness of the provided formula.

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  • Understanding of parabolic geometry and properties
  • Familiarity with the concepts of focus and directrix
  • Knowledge of standard forms of conic sections
  • Basic algebraic manipulation skills
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  • Study the derivation of the standard form of parabolas
  • Learn about the properties of conic sections in analytical geometry
  • Explore the relationship between focus, directrix, and vertex in parabolas
  • Investigate applications of parabolas in physics and engineering
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For a parabola whose Directrix is given by the equation x=p and whose Focus is (h,k).

Is this by any chance the correct general form of the parabola?

x=1/2(h-p) [y^2 - 2yk + h^2+k^2-p^2]
 
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you_of_eh said:
For a parabola whose Directrix is given by the equation x=p and whose Focus is (h,k).

Is this by any chance the correct general form of the parabola?

x=1/2(h-p) [y^2 - 2yk + h^2+k^2-p^2]
The vertex of a parabola is halfway between the focus and directrix. Here, that is at ((h+p)/2, k) so the focal length is (h+p)/2- p= (h-p)/2. Since the "standard" parabola, with horizontal axis, is 4d(x- x_0)= (y- y_0)^2, here that would be [4(h-p)/2](x- (h+p)/2)= (y- k)^2 which can be written as x= \frac{1}{2(h-p)}(y- k)^2+ \frac{h+p}{2}. If you take that "(h+p)/2" inside the parentheses you get exactly what you have. Well done!
 
Alright perfect! thanks a lot for your time.
 

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