Math Problem Statement

I. Graphing Parabolas: Graph the following equations in a rectangular coordinate plane. Then, identify the required properties being asked in each item.

  1. 3y^2 - 18y + 12x + 3 = 0 Standard Form: Opening: Vertex: Distance between the vertex and focus: Focus: Equation of Axis of Symmetry: Length of Lactus Rectum: Endpoints of Latus Rectum: Equation of Directrix:

Solution

To solve the given problem and extract the properties of the parabola, we will start by rewriting the equation in a standard form and then derive each required property step by step.

The given equation is: 3y218y+12x+3=03y^2 - 18y + 12x + 3 = 0

Step 1: Rewrite in Standard Form

We begin by isolating the terms involving xx and yy, focusing on making the quadratic term in yy appear as part of a perfect square.

3y218y+12x+3=03y^2 - 18y + 12x + 3 = 0 Move 12x+312x + 3 to the other side: 3y218y=12x33y^2 - 18y = -12x - 3 Factor out the 3 from the terms on the left-hand side: 3(y26y)=12x33(y^2 - 6y) = -12x - 3 Complete the square inside the parentheses. To complete the square, take half of the coefficient of yy, square it, and add and subtract the same value inside the equation. Here, half of 6-6 is 3-3, and (3)2=9(-3)^2 = 9.

Add and subtract 9 inside the parentheses: 3[(y26y+9)9]=12x33[(y^2 - 6y + 9) - 9] = -12x - 3 Simplify this: 3(y3)227=12x33(y - 3)^2 - 27 = -12x - 3 Now move 27-27 to the right-hand side: 3(y3)2=12x+243(y - 3)^2 = -12x + 24 Finally, divide through by 3 to get the equation into standard form: (y3)2=4(x2)(y - 3)^2 = -4(x - 2) This is the equation of a parabola in standard form (yk)2=4p(xh)(y - k)^2 = 4p(x - h), which opens horizontally.

Step 2: Identify Properties

  1. Standard Form:
    (y3)2=4(x2)(y - 3)^2 = -4(x - 2)

  2. Opening:
    Since the coefficient of (y3)2(y - 3)^2 is negative, the parabola opens left.

  3. Vertex:
    The vertex is (h,k)(h, k), which corresponds to (2,3)(2, 3).

  4. Distance between the vertex and focus (p):
    From the standard form, 4p=44p = -4, so p=1p = -1.
    The distance between the vertex and the focus is 1 unit.

  5. Focus:
    The focus lies 1 unit to the left of the vertex, as the parabola opens left.
    So, the focus is at (21,3)=(1,3)(2 - 1, 3) = (1, 3).

  6. Equation of Axis of Symmetry:
    The axis of symmetry is the horizontal line passing through the vertex.
    The equation is y=3y = 3.

  7. Length of Latus Rectum:
    The length of the latus rectum is 4p=4|4p| = 4 units.

  8. Endpoints of Latus Rectum:
    The endpoints of the latus rectum are 2 units above and 2 units below the focus (since the length is 4 units and is symmetric about the focus).
    The endpoints are (1,3+2)=(1,5)(1, 3 + 2) = (1, 5) and (1,32)=(1,1)(1, 3 - 2) = (1, 1).

  9. Equation of Directrix:
    The directrix is a vertical line located p=1p = 1 unit to the right of the vertex, at x=2+1=3x = 2 + 1 = 3.
    The equation of the directrix is x=3x = 3.

Summary of Properties:

  • Standard Form: (y3)2=4(x2)(y - 3)^2 = -4(x - 2)
  • Opening: Left
  • Vertex: (2,3)(2, 3)
  • Distance between Vertex and Focus: 1 unit
  • Focus: (1,3)(1, 3)
  • Equation of Axis of Symmetry: y=3y = 3
  • Length of Latus Rectum: 4 units
  • Endpoints of Latus Rectum: (1,5)(1, 5) and (1,1)(1, 1)
  • Equation of Directrix: x=3x = 3

Would you like any further clarification or details?

Related Questions:

  1. How do we find the equation of a parabola if given its focus and directrix?
  2. How does the direction of the parabola's opening change with the coefficient of xx or yy?
  3. What is the significance of the latus rectum in parabola geometry?
  4. How can we determine the focal distance in more complex conic sections like ellipses and hyperbolas?
  5. How does completing the square help in deriving the standard form of a conic?

Tip:

When graphing a parabola, always start by identifying the vertex, as it serves as the foundation for determining the focus, directrix, and other key features.

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Math Problem Analysis

Mathematical Concepts

Conic Sections
Parabolas
Quadratic Equations
Graphing

Formulas

Standard form of a parabola: (y - k)^2 = 4p(x - h)
Formula for completing the square: (b/2)^2
Distance formula for vertex and focus: p

Theorems

Parabola Equation Theorem
Axis of Symmetry Theorem
Latus Rectum Property of Parabolas

Suitable Grade Level

Grades 10-12