Math Problem Statement

Rewrite the ellipse equation 16x^2 + 9y^2 - 64x - 108y + 244 = 0 in standard form and find its key parameters.

Solution

Let's analyze and solve the given problem. We are tasked with rewriting the ellipse equation in standard form and then extracting key details.


Step 1: Rewrite the ellipse equation in standard form

The given equation is:

16x2+9y264x108y+244=016x^2 + 9y^2 - 64x - 108y + 244 = 0

Group and complete the square for xx and yy:

  1. Group xx terms and yy terms:

    16(x24x)+9(y212y)=24416(x^2 - 4x) + 9(y^2 - 12y) = -244

  2. Complete the square for xx:

    For x24xx^2 - 4x, the coefficient of xx is 4-4. Half of 4-4 is 2-2, and squaring it gives 44.

    Add and subtract 44 inside the parentheses:

    16(x24x+44)=16((x2)24)16(x^2 - 4x + 4 - 4) = 16((x - 2)^2 - 4)

    This simplifies to:

    16(x2)26416(x - 2)^2 - 64

  3. Complete the square for yy:

    For y212yy^2 - 12y, the coefficient of yy is 12-12. Half of 12-12 is 6-6, and squaring it gives 3636.

    Add and subtract 3636 inside the parentheses:

    9(y212y+3636)=9((y6)236)9(y^2 - 12y + 36 - 36) = 9((y - 6)^2 - 36)

    This simplifies to:

    9(y6)23249(y - 6)^2 - 324

  4. Rewrite the equation with completed squares:

    Substituting back, we get:

    16(x2)264+9(y6)2324=24416(x - 2)^2 - 64 + 9(y - 6)^2 - 324 = -244

    Combine constants:

    16(x2)2+9(y6)2388=24416(x - 2)^2 + 9(y - 6)^2 - 388 = -244

    Add 388388 to both sides:

    16(x2)2+9(y6)2=14416(x - 2)^2 + 9(y - 6)^2 = 144

  5. Divide through by 144 to normalize:

    16(x2)2144+9(y6)2144=1\frac{16(x - 2)^2}{144} + \frac{9(y - 6)^2}{144} = 1

    Simplify the denominators:

    (x2)29+(y6)216=1\frac{(x - 2)^2}{9} + \frac{(y - 6)^2}{16} = 1


Step 2: Identify the ellipse parameters

From the standard form:

(xh)2a2+(yk)2b2=1\frac{(x - h)^2}{a^2} + \frac{(y - k)^2}{b^2} = 1

we can identify:

  • h=2h = 2
  • k=6k = 6
  • a2=16    a=4a^2 = 16 \implies a = 4
  • b2=9    b=3b^2 = 9 \implies b = 3

Since a>ba > b, the major axis is vertical.


Step 3: Find the endpoints of the axes

Major axis (vertical):

The major axis is along y=k=6y = k = 6. The endpoints are:

(x,y)=(2,6±a)=(2,6+4) and (2,64)(x, y) = (2, 6 \pm a) = (2, 6 + 4) \text{ and } (2, 6 - 4)

Endpoints:

(2,10)and(2,2)(2, 10) \quad \text{and} \quad (2, 2)

Minor axis (horizontal):

The minor axis is along x=h=2x = h = 2. The endpoints are:

(x,y)=(2±b,6)=(2+3,6) and (23,6)(x, y) = (2 \pm b, 6) = (2 + 3, 6) \text{ and } (2 - 3, 6)

Endpoints:

(5,6)and(1,6)(5, 6) \quad \text{and} \quad (-1, 6)


Step 4: Foci of the ellipse

The foci lie along the major axis at a distance of cc from the center, where:

c=a2b2=169=7c = \sqrt{a^2 - b^2} = \sqrt{16 - 9} = \sqrt{7}

Thus, the foci are:

(x,y)=(2,6±7)(x, y) = (2, 6 \pm \sqrt{7})


Final Answer:

  • Standard form: (x2)29+(y6)216=1\frac{(x - 2)^2}{9} + \frac{(y - 6)^2}{16} = 1
  • Center (h,kh, k): (2,6)(2, 6)
  • a=4a = 4, b=3b = 3
  • Major axis endpoints: (2,10)(2, 10) and (2,2)(2, 2)
  • Minor axis endpoints: (5,6)(5, 6) and (1,6)(-1, 6)
  • Foci: (2,6+7)(2, 6 + \sqrt{7}) and (2,67)(2, 6 - \sqrt{7})

Would you like further clarification on any step?


Explore Further:

  1. What is the formula for the eccentricity of an ellipse?
  2. How do we determine whether an ellipse is horizontal or vertical?
  3. Can the minor axis ever be longer than the major axis?
  4. How does completing the square help in deriving the standard form of conic sections?
  5. What is the geometric meaning of the foci?

Tip: Always confirm whether a2a^2 or b2b^2 is larger to correctly identify the major axis of an ellipse!

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Math Problem Analysis

Mathematical Concepts

Algebra
Conic Sections
Ellipses
Completing the Square
Standard Form of Ellipse

Formulas

\frac{(x - h)^2}{a^2} + \frac{(y - k)^2}{b^2} = 1
c = \sqrt{a^2 - b^2}

Theorems

Equation of an Ellipse in Standard Form
Completing the Square

Suitable Grade Level

Grades 10-12