This tutorial demonstrates how to find the points of intersection of two ellipses given by their equations using algebraic elimination and substitution techniques.
Example 1
Find the points of intersection of the two ellipses given by their equations as follows:
\[ \dfrac{x^2}{16} + \dfrac{(y + 1)^2}{4} = 1 \] \[ \dfrac{x^2}{2} + \dfrac{(y + 2)^2}{12} = 1 \]View Solution
We first multiply all terms of the first equation by \( 16 \) and all the terms of the second equation by \( -2 \) and simplify to obtain equivalent equations given by:
\[ x^2 + 4(y + 1)^2 = 16 \] \[ -x^2 - \dfrac{1}{6}(y + 2)^2 = -2 \]We now add side by side the two equations to eliminate \( x^2 \) and obtain a quadratic equation in terms of \( y \):
\[ 4(y + 1)^2 - \dfrac{1}{6}(y + 2)^2 = 14 \]Multiply all terms by 6, group like terms, and rewrite the equation in standard quadratic form:
\[ 23y^2 + 44y - 64 = 0 \]Solve the quadratic equation for \( y \) using the quadratic formula to obtain two solutions:
\[ y \approx 0.97 \quad \text{and} \quad y \approx -2.88 \]We now substitute the values of \( y \) already obtained into the equation \( x^2 + 4(y + 1)^2 = 16 \) and solve it for \( x \) to obtain the corresponding \( x \) values:
- For \( y \approx 0.97 \): \( x \approx 0.730365 \) and \( x \approx -0.730365 \)
- For \( y \approx -2.88 \): \( x \approx 1.36788 \) and \( x \approx -1.36788 \)
Thus, the 4 points of intersection of the two ellipses are:
\[ (0.73, 0.97), \quad (-0.73, 0.97), \quad (1.37, -2.88), \quad (-1.37, -2.88) \]The graph of the two ellipses and their intersection points is shown below:
More Links and References on Ellipses
- Points of Intersection of an Ellipse and a line
- Find the Points of Intersection of a Circle and an Ellipse
- Equation of Ellipse, Problems
- College Algebra Problems With Answers - Sample 8: Equation of Ellipse
- HTML5 Applet to Explore Equations of Ellipses
- Ellipse Area and Perimeter Calculator
- Home Page