Math Problem Statement

Find the equation of the circle passing through (-3,6) , (-5,2) and (3, -6).

Solution

To find the equation of the circle passing through the points (3,6)(-3, 6), (5,2)(-5, 2), and (3,6)(3, -6), we can use the general equation of a circle:

x2+y2+Dx+Ey+F=0x^2 + y^2 + Dx + Ey + F = 0

where DD, EE, and FF are constants that need to be determined.

Step 1: Substituting the points into the equation

We substitute each point into the general equation:

  1. For (3,6)(-3, 6): (3)2+(6)2+D(3)+E(6)+F=0(-3)^2 + (6)^2 + D(-3) + E(6) + F = 0 9+363D+6E+F=09 + 36 - 3D + 6E + F = 0 \quad \text{(Equation 1)}$$
  2. For (5,2)(-5, 2): (5)2+(2)2+D(5)+E(2)+F=0(-5)^2 + (2)^2 + D(-5) + E(2) + F = 0 25+45D+2E+F=025 + 4 - 5D + 2E + F = 0 \quad \text{(Equation 2)}$$
  3. For (3,6)(3, -6): (3)2+(6)2+D(3)+E(6)+F=0(3)^2 + (-6)^2 + D(3) + E(-6) + F = 0 9+36+3D6E+F=09 + 36 + 3D - 6E + F = 0 \quad \text{(Equation 3)}$$

Step 2: Solving the system of equations

We now solve the system of equations formed by:

  1. 453D+6E+F=045 - 3D + 6E + F = 0
  2. 295D+2E+F=029 - 5D + 2E + F = 0
  3. 45+3D6E+F=045 + 3D - 6E + F = 0

Let's solve this step-by-step. I'll continue by eliminating FF.The solution to the system of equations is:

  • D=4D = -4
  • E=2E = -2
  • F=45F = -45

Step 3: Writing the equation of the circle

Substituting these values into the general equation of a circle:

x2+y2+Dx+Ey+F=0x^2 + y^2 + Dx + Ey + F = 0

we get:

x2+y24x2y45=0x^2 + y^2 - 4x - 2y - 45 = 0

Thus, the equation of the circle is:

x2+y24x2y45=0x^2 + y^2 - 4x - 2y - 45 = 0

Would you like a detailed explanation of any part of this solution? Here are some related questions for further exploration:

  1. How do you find the radius of the circle given the equation?
  2. Can we convert this equation into center-radius form?
  3. How would we determine if a point lies inside the circle?
  4. What is the geometric significance of the constants DD and EE?
  5. How do you generalize this method for any three points?

Tip: The general form of a circle equation x2+y2+Dx+Ey+F=0x^2 + y^2 + Dx + Ey + F = 0 can be easily converted into center-radius form to identify the center and radius directly.

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Math Problem Analysis

Mathematical Concepts

Analytic Geometry
Equations of Circles
Systems of Linear Equations

Formulas

General form of the equation of a circle: x^2 + y^2 + Dx + Ey + F = 0

Theorems

System of Linear Equations (for solving D, E, F)
Circle Equation Theorem

Suitable Grade Level

Grades 10-12