Write the equation of the parabola with a focus of (6,−5) and directrix of x=2 . Note: Enter your answer and SHOW ALL THE STEPS NECESSARY to solve this problem in the space provided. You will not receive credit without all work shown.

1 answer

To find the equation of the parabola with a focus at \((6, -5)\) and a directrix of \(x = 2\), we will follow the standard definition and properties of a parabola.

Step 1: Identify the Properties

  1. Focus: The focus of the parabola is at the point \((6, -5)\).
  2. Directrix: The directrix of the parabola is the vertical line \(x = 2\).
  3. Vertex: The vertex of the parabola is located halfway between the focus and the directrix.

Step 2: Calculate the Vertex

The vertex \(V\) is the average of the x-coordinates of the focus and the directrix line.

  • x-coordinate of the focus: \(6\)
  • Equation of the directrix: \(x = 2\)

The vertex \(x\) coordinate is calculated as follows: \[ x_V = \frac{6 + 2}{2} = \frac{8}{2} = 4 \] The y-coordinate of the vertex is the same as the y-coordinate of the focus since the focus is not vertically aligned with the directrix. Therefore, \[ y_V = -5 \] So the vertex is \((4, -5)\).

Step 3: Determine the Orientation

Since the directrix is a vertical line, the parabola will open to the right or to the left. Since the focus \((6, -5)\) is to the right of the directrix \(x = 2\), the parabola opens to the right.

Step 4: Find the Distance \(p\)

The distance \(p\) is the distance from the vertex to the focus (or from the vertex to the directrix). We can find this distance by calculating:

\[ p = 6 - 4 = 2 \]

Step 5: Write the Standard Form of the Parabola

The standard form of the equation of a horizontally oriented parabola (opening to the right) with vertex \((h, k)\) is: \[ (y - k)^2 = 4p(x - h) \] Where \((h, k)\) is the vertex and \(p\) is the distance from the vertex to the focus.

Plugging the vertex \((4, -5)\) and \(p = 2\) into the formula:

  • \(h = 4\)
  • \(k = -5\)
  • \(4p = 4 \cdot 2 = 8\)

Step 6: Write the Equation of the Parabola

The equation of the parabola becomes: \[ (y + 5)^2 = 8(x - 4) \]

Thus, the final equation of the parabola is: \[ \boxed{(y + 5)^2 = 8(x - 4)} \]