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If a parabola has its focus at the origin and the \(x\) axis is its axis, prove that it must have an equation of the form \(y^{2}=4 k x+4 k^{2}, k \neq 0\).

Short Answer

Expert verified
The equation of the parabola is y^2 = 4kx + 4k^2, where k > 0.

Step by step solution

01

Understanding the Geometry

The focus of the parabola is at the origin the coordinates are (0, 0), and the axis is the x-axis.
02

Standard Form of Parabola Equation

The standard equation for a parabola that opens to the right or left (with the x-axis as the axis) is y^2 = 4ax.The parameter 'a' is the distance from the vertex to the focus,.
03

Translate the Parabola

Since the focus is at the origin and not at 'a' on the x-axis, this implies the vertex is not at the origin.Consider the vertex be at (-k, 0); the focus being at (0, 0).The vertex is thus k units to the left of the focus.
04

Modified Equation

Given the vertex at (-k, 0) for a similar parabola opening rightwardthe transformed equation is (y - 0)^2 = 4k(x + k).
05

Simplify the Equation

Expanding and simplifying, y^2 = 4kx + 4k^2.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Parabola Equation
To understand the equation of a parabola, we need to first grasp its basic form. For parabolas that open either to the left or right along the x-axis, the standard form is given by: \[ y^2 = 4ax \]Here, 'a' represents the distance from the vertex of the parabola to its focus. This relationship helps in setting the stage to derive other variations of the equation. If the vertex is shifted from its original location, this basic equation can be modified to accommodate the shift, which brings us to our next concept: transforming the parabola equation.
Focus and Vertex Relationship
To solve the problem, we need to understand the relationship between the vertex and the focus of a parabola. If the focus is at the origin \((0, 0)\) and the vertex is not at the origin but rather shifted to \((-k, 0)\), then the configuration changes the equation. This transformation means that the vertex is k units to the left of the focus on the x-axis. To incorporate this shift into our equation, we need to adjust for the vertex's new position. This goes from the standard form to:\[ (y - 0)^2 = 4a(x + k) \]Which translates to \((y)^2 = 4k(x + k)\).Finally, expanding this you get:\[ y^2 = 4kx + 4k^2\]This derived equation fits our original scenario, with the focus at the origin and the vertex moved to \((-k, 0)\).
Parabola Transformation
Transforming the parabola means shifting its vertex while maintaining the focus. For the given exercise, the vertex is at \((-k, 0)\) while the focus remains at \((0, 0)\). The transformation modifies the standard equation \((y^2 = 4ax)\) into a new form. Hence, the transformation process involves:
  • Recognizing the vertex shift
  • Adjusting the equation accordingly
  • Expanding and simplifying
So, starting with the standard form and incorporating the shift, we get the modified equation: \[(y - 0)^2 = 4a(x + k)\]. Further simplification yields similar terms added to the original equation, converting it to: \[ y^2 = 4kx + 4k^2 \] This derived equation expresses a parabola whose focus is at the origin and the vertex is shifted horizontally.

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