Math Problem Statement

Difference of a equation of a circle and a line by using a problem

Solution

Certainly! Let's go through an example problem that involves both the equation of a circle and the equation of a line. We'll then find their points of intersection, which will illustrate the difference between the two equations.

Problem Example:

Find the points of intersection between the circle x2+y2=25x^2 + y^2 = 25 and the line y=3x+1y = 3x + 1.

Step-by-Step Solution:

  1. Equation of the Circle: x2+y2=25x^2 + y^2 = 25 This represents a circle with a center at the origin (0,0) and a radius of 5.

  2. Equation of the Line: y=3x+1y = 3x + 1 This represents a line with a slope of 3 and a y-intercept of 1.

  3. Substitute the Line Equation into the Circle Equation: To find the points of intersection, we need to substitute yy from the line equation into the circle equation: x2+(3x+1)2=25x^2 + (3x + 1)^2 = 25

  4. Expand and Simplify: x2+(3x+1)2=25x^2 + (3x + 1)^2 = 25 x2+(9x2+6x+1)=25x^2 + (9x^2 + 6x + 1) = 25 x2+9x2+6x+1=25x^2 + 9x^2 + 6x + 1 = 25 10x2+6x+1=2510x^2 + 6x + 1 = 25 10x2+6x+125=010x^2 + 6x + 1 - 25 = 0 10x2+6x24=010x^2 + 6x - 24 = 0

  5. Solve the Quadratic Equation: Use the quadratic formula x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}, where a=10a = 10, b=6b = 6, and c=24c = -24: x=6±62410(24)210x = \frac{-6 \pm \sqrt{6^2 - 4 \cdot 10 \cdot (-24)}}{2 \cdot 10} x=6±36+96020x = \frac{-6 \pm \sqrt{36 + 960}}{20} x=6±99620x = \frac{-6 \pm \sqrt{996}}{20} x=6±224920x = \frac{-6 \pm 2\sqrt{249}}{20} x=3±24910x = \frac{-3 \pm \sqrt{249}}{10}

  6. Find the Corresponding yy Values: Substitute xx back into the line equation y=3x+1y = 3x + 1: y=3(3+24910)+1y = 3 \left(\frac{-3 + \sqrt{249}}{10}\right) + 1 y=9+324910+1y = \frac{-9 + 3\sqrt{249}}{10} + 1 y=9+3249+1010y = \frac{-9 + 3\sqrt{249} + 10}{10} y=1+324910y = \frac{1 + 3\sqrt{249}}{10}

    Similarly, y=3(324910)+1y = 3 \left(\frac{-3 - \sqrt{249}}{10}\right) + 1 y=9324910+1y = \frac{-9 - 3\sqrt{249}}{10} + 1 y=93249+1010y = \frac{-9 - 3\sqrt{249} + 10}{10} y=1324910y = \frac{1 - 3\sqrt{249}}{10}

So, the points of intersection are: (3+24910,1+324910)and(324910,1324910)\left( \frac{-3 + \sqrt{249}}{10}, \frac{1 + 3\sqrt{249}}{10} \right) \quad \text{and} \quad \left( \frac{-3 - \sqrt{249}}{10}, \frac{1 - 3\sqrt{249}}{10} \right)

Summary:

  • The circle's equation represents all points equidistant from a center point.
  • The line's equation represents all points along a path with a constant slope.
  • The points of intersection are found by solving the system of equations formed by the circle and the line.

Would you like more details or have any questions?

Relative Questions:

  1. How do you derive the general form of the equation of a circle from its center and radius?
  2. What are the properties of the slope-intercept form of a linear equation?
  3. Can a line intersect a circle at more than two points? Why or why not?
  4. How does completing the square help in finding the center and radius of a circle given its general equation?
  5. What are some real-life applications where solving the intersection of a circle and a line is useful?

Tip:

When solving the intersection of a circle and a line, always check for extraneous solutions by substituting back into both original equations to verify the points.

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Math Problem Analysis

Mathematical Concepts

Geometry
Equations of Circles
Equations of Lines
Intersection of Geometric Figures
Quadratic Equations

Formulas

Quadratic formula

Theorems

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Suitable Grade Level

Grades 10-12