This tutorial demonstrates how to find the points of intersection of an ellipse and a line given by their equations using substitution and algebraic solving techniques.
Example 1
Find the points of intersection of an ellipse and a line given by their equations as follows:
\[ \dfrac{x^2}{9} + \dfrac{y^2}{4} = 1 \] \[ y - 2x = -2 \]View Solution
We first solve the equation of the line for \( y \) to obtain:
\[ y = 2x - 2 \]We now substitute \( y \) with \( 2x - 2 \) in the equation of the ellipse:
\[ \dfrac{x^2}{9} + \dfrac{(2x - 2)^2}{4} = 1 \]Multiply all terms by 36, group like terms, and rewrite the equation as:
\[ 40x^2 - 72x = 0 \]Solve the quadratic equation for \( x \) to obtain two solutions:
\[ x = 0 \quad \text{and} \quad x = \dfrac{9}{5} \]We now substitute the values of \( x \) already obtained into the equation \( y = 2x - 2 \) and find \( y \):
- For \( x = 0 \): \( y = 2(0) - 2 = -2 \)
- For \( x = \dfrac{9}{5} \): \( y = 2\left(\dfrac{9}{5}\right) - 2 = \dfrac{18}{5} - \dfrac{10}{5} = \dfrac{8}{5} \)
There are 2 points of intersection given by:
\[ (0, -2) \quad \text{and} \quad \left(\dfrac{9}{5}, \dfrac{8}{5}\right) \]The graphs of the ellipse and the line given by their equations above and their points of intersection are shown below:
More Links and References on Ellipses
- Find the Points of Intersection of two Ellipses
- 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